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Introduction

The air is a fundamental element of planet Earth that sustains life. The broad term “air” is used to describe the mixture of gases that makes up the earth’s atmosphere. It is a clear gas required for breathing and performing regular cellular activities. Air is a very essential and makes up the atmosphere of the earth.

It has the following other applications-

• All life depends on air to thrive, including humans, plants, animals, and other species.
• The air is necessary for the water cycle to take place.
• It facilitates combustion and breathing.
• It keeps the temperature constant.
• Air assists in the process of pollination in wind-pollinated plants.

Components of Air

The air around is composed of various components given below-

• Oxygen makes up around 21% of the air.
• The highest amount of gas present in the air is Nitrogen, which makes up 78% of the total air.
• Argon is 0.9% of the total air.
• Carbon dioxide is the lowest around 0.04% of the air.
• There are still other gases which are present in very lower concentrations eg. water vapour.
• Microscopic airborne particles known as “aerosols”  are also present in the air and are present in minute quantities.
• These aerosols include bacteria, suspended dust, pollen, and spores.

Properties of Air

• Air is colourless and odourless and cannot be seen, heard or touched.
• It is a mixture of many gases and they occupy space and matter.
• Air exerts pressure. Near the surface, the air pressure is more and at higher altitudes the air pressure is low.
• When heated the air expands and when cooled the air compresses.

Uses of Air

Respiration

• Respiration is the process where gaseous exchange occurs and oxygen is inhaled and carbon dioxide is exhaled.
• The two main gases involved in respiration are carbon dioxide and oxygen.
• Plants and animals require oxygen to convert the chemical energy found in food into energy that can be used for various metabolic processes.
• This energy is used in all actions of growth, development, locomotion and reproduction.
• Oxygen is created through the process of photosynthesis, which occurs when plants use carbon dioxide to make chemical energy while utilizing light energy.
  

Combustion

• A fuel oxidises when it is burned and produces lots of energy.
• This is an exothermic reaction wherein light and heat are generated.
• Any carbon-containing substance that is burned in the presence of oxygen produces carbon dioxide, water vapour, heat, and light energy.
• Colourful flames are created when methane, an essential element of combustion, combines with air. These colourful flames are an indicator of the combustion reaction.
• Explosive burning might occur if there is too much oxygen present hence to prevent this nitrogen gas is present in the atmosphere.
• Nitrogen does not contribute to combustion and inhibits too much oxygen from causing higher reactivity. Therefore, these two components work together to make sure that fuel energy is used in a controlled way.
• The heat that is generated during the process of combustion is used to cook, run our vehicles, generate electricity etc.

Regulation of temperature

• The earth’s surface is kept at a constant temperature by air.
• The density of hot air is less and hence it rises above the ground. This leads to the formation of a low-pressure area which is quickly filled by cool air.
• This phenomenon leads to the formation of winds.
• As the temperature of the air rises the air moves up draws in cooler air from the surroundings, warms it up, and the cycle repeats.
• When hot air rises, it radiates heat into space before sinking back to earth.
• Convection is the process of moving heat, and this is referred to as temperature regulation.
• Heat is transferred in this way from hotter to colder places and thus the temperature of the earth is regulated.
• The atmosphere and air also help to cool the earth and protect it from the sun’s excessive UV rays.

Summary

Air surrounding the earth makes up its atmosphere. The air is a mixture of gases and is essential to many living things. Air consists of 78% of nitrogen, 21% oxygen, 0.9% argon, and 0.04% carbon dioxide, and there are traces of other gases as well. The thick layer of air supports vital life-supporting activities. Contrarily, air is a substance and it has mass, can be compressed, and takes up space. Air performs the following major processes—breathing, combustion, and regulating the earth’s temperature.

Frequently Asked Question

1. Give the function of the ozone layer
Ans: The ozone layer, which is found in the stratosphere of the earth and absorbs the majority of the sun’s ultraviolet rays, works as a screen to protect the planet from these rays.

2. What does acid rain mean?
Ans: Polluted air consists of oxides of nitrates and sulphates. These oxides react with water vapour and other air components to form sulfuric acid and nitric acid. When there is rainfall both of these acids fall on earth which is termed acid rain. This acid rain is not only harmful to people but also affects various other living organisms.

3. What are the ill effects of air pollution?
Ans: Air pollution is a very severe problem that aggravates pre-existing respiratory and cardiac problems and causes several pollution-related ailments. Common diseases caused due by air pollution are lung cancer, stroke, chronic obstructive pulmonary disease (COPD), and respiratory infections.

Introduction

In the farming and agricultural sectors, the tools used to streamline the process are referred to as agricultural implements. To create a productive and helpful environment, agricultural operations today require a different range of tools, such as drills, diggers, furrows, sickles, and so on. Without the use of the implements that are supposed to finish these processes, the current situation in agriculture demonstrates development. In this tutorial, we’ll discuss agricultural equipment and how they affect the farming and agricultural industries.

What is Agriculture?

Agriculture is the activity of growing crops and rearing animals that supports human sedentary behavior and the growth of sustenance. It may be involved in the production, processing, and distribution of agricultural products. For most rural communities, it serves as their primary source of income. In metropolitan regions, individuals are provided with vegetables and grains for food.

Significance of Agriculture

• The majority of the world’s food supply comes from agriculture, which also guarantees the population’s access to food and nourishment. 
• Since agriculture contributes over 20% of GDP (Gross Domestic Product), it is regarded as the main source of income for the nation. 
• A large number of people have employment opportunities in agriculture. 
• It plays a significant part in the export of significant goods on a global scale and in balancing a nation’s crucial expenditures while preserving its foreign currency. 
• Additionally, it generates fibers, raw materials, and biofuels.
• Utilizing the production and selling of agricultural goods eliminates poverty in rural regions. 
• Selling the by-products of raising animals brings considerable profit for farmers.

What are Agricultural Implements?

Agriculture implements and farming equipment are tools or pieces of machinery used to complete tasks quickly. These are used in agriculture to lessen physical labor and increase crop output. Early farmers developed their own labor and time-intensive tools, which were difficult to use. After modernization, cutting-edge processes and tools have taken the place of outdated ones.

To make work easier, a variety of agricultural implements are used in agriculture. The following is a list of important agricultural tools: 

• Planting tools 
• Harvesting equipment
• Irrigation equipment
• Tools for cultivating soil

Types of Agricultural Implements

Farmers employ a variety of agricultural instruments to increase crop yield. It includes the following:

Soil cultivation implements

• The cultivation of the soil is a crucial stage because it enables crop roots to enter the soil and absorb nutrients and water. 
• Soil preparation is done with basic equipment like a hoe, a plow, and cultivators. 
• The land is plowed and made ready for cultivation with the use of spike, drag, and disc harrows.

Irrigation machines

It is made up of a pump that draws water from the bottom and a pivot irrigation system that supplies the crops with the right amount of water.

Planting machines

• The plant is protected from animals and birds attack by the use of a seed drill, which provides a deep and proper area for planting. 
• It enables the plants to receive enough sunlight, nutrients, and water. 
• After crop cultivation, a large area is seeded using tools including air seeders, broadcast seeders, transplanting implements, and more.

Harvesting implements

• Cutting fully developed and ripe crops is the procedure of harvesting. 
• Crops are harvested using harvesting equipment like pickers, trailers, and diggers.

Division of Crops

The agricultural process develops food grains for human consumption and utilizes their raw materials for industrial use. Crops are cultivated according to the type of soil and weather conditions. There are three major divisions of crops. 

Kharif crop

• In the monsoon season, the seedlings of crops begin to grow and are harvested in the autumn.
• A warm climate and excess water are necessary for its growth.

Rabi crop

• In humid conditions, seeds germinate and develop well, and crops grow well. 

Zaid crop

• During the period between Kharif and Rabi, the Zaid crop develops.
• For blooming flowers, warm, dry weather is required for crop growth.

Type of crop	Season	Examples
Kharif crop	September to October	Millets. maize, rice, soybean, cotton
Rabi crop	October to December and April to May	Barley, oats, mustard, wheat, peas
Zaid crop	March to June	Watermelon, cucumber, muskmelon, pumpkin, pulses

Categories of Crops

Depending on their use, crops can be classified into two types.

• Food crops: Food crops are mainly grown for human and animal consumption. There are several major food crops, such as vegetables, oilseeds such as sunflower, groundnut, sesame, and cereals like paddy, wheat, and fruits.
• Cash crops: Crops that are grown to generate income rather than for domestic consumption are called cash crops. Rubber, tea, coffee, jute, spices like mustard, chili, turmeric, garlic, coriander, and some medicinal crops are some of the most important cash crops.

Summary

Agriculture implements and farming equipment are tools or pieces of machinery used to complete tasks quickly. Farmers employ a variety of agricultural instruments to increase crop yield.  The agricultural process develops food grains for human consumption and utilizes their raw materials for industrial use. Depending on their use, crops can be classified into two types such as food crops and cash crops.

Frequently Asked Questions

1. How does agriculture have such a big impact on a nation?
Ans. A nation’s economy is based on agriculture because it provides food, is a source of commercial products, creates employment, and eliminates poverty. More than half of the population solely depends on agriculture for a living.

2. Why are outdated agricultural equipment and practises replaced?
Ans. In addition to hand-made tools, traditional techniques are tedious and time-consuming. Therefore, advanced techniques and equipment are used to increase crop production quickly. 

3. What farming tools are used to get the soil ready for cultivation?
Ans. Disc harrows, drags, and hoes are agricultural implements used to plow the soil, allowing roots to penetrate the ground and absorb moisture and nutrients more easily.

4. What kinds of crops are grown during the monsoon and summer seasons?
Ans. Kharif crops are produced in the monsoon season of September and October. Zaid crops are produced in the summer season, from March to June. Rabi crops are also produced in the summer, from April to May.

5. What are the main tools used in agriculture?
Ans. Machines for planting, harvesting, irrigating, and cultivating the soil are the most important agricultural implements. The use of these is widespread in organic farming and commercial agriculture.

Introduction

We know that a capacitor consists of two plates of conductors separated by an isolated distance and is also known as a dielectric. The capacitor limits or regulates the current when connected to an alternating current source, but it does not completely prevent charge drift. The capacitor gradually charges and discharges as the current reverses throughout each half-cycle. The highest charging current occurs while the capacitor’s plates are not charged, hence the charging process is not linear or instantaneous. Similar to the capacitor, once it is completely charged, its charge starts to drop dramatically. The capacity of a capacitor to hold a charge on its plates is known as capacitance. When a capacitor is connected to a voltage source in a DC circuit, current flows for the brief period of time required to charge the capacitor. The voltage across the conductive plates increases as charge accumulates on them, reducing the current. The circuit current zeroes out after the capacitor is fully charged.

Capacitance in AC circuits and capacitive reactance

A capacitor’s estimated capacity to store energy in an AC circuit is known as capacitance. The ratio of an electric charge to the corresponding difference in its electric potential is known as capacitance.

$$C=\frac{d Q}{d V}$$

Where dQ and dV are the charge and potential difference across capacitors, respectively. The capacitance may also be defined as the property of a capacitor to store the charge. The correlation between charging current (I) and the capacitors at which the capacitors supply voltage changes is given by 

$$I=C \frac{d Q}{d V}$$

Capacitive reactance

Capacitive reactance is the resistance to the flow of electricity through the AC capacitor. It is calculated in ohm and denoted by \(X_C\) and measured in the units of Ω. It is calculated mathematically using the provided formula.

$$X_C=\frac{1}{2 \pi f C}=\frac{1}{\omega C}$$

Where f is the frequency, C is the capacitance and ⍵=2πf.

The ratio of the effective current to the voltage across the capacitor is another way to describe the capacitive reactance. We get the conclusion that capacitive reactance is inversely linked to frequency from the aforementioned connection. This implies that a drop in frequency across the capacitor will result in a decrease in capacitive reactance, and vice versa.

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How does a capacitor work in AC?

The capacitor is directly linked to the AC supply in an AC circuit. The capacitor goes through a process of charging or discharging and blocks DC when an AC source is applied. The capacitor also partially obstructs the AC signal. Reactance is the term used to describe a capacitor’s properties in reaction to an AC signal. The capacitor has a short circuit in AC.

AC Capacitor Circuits?

An AC capacitor circuit directly connects the AC supply to the capacitor to allow current to flow through the circuit. The capacitor’s plates are constantly being charged and discharged as a result of the AC supply.

Role of capacitor in AC circuit

As long as there is a source, the capacitor will constantly charge and discharge. The time constant, however, governs whether it fully charges (transforms electrical energy into charge to store between two plates) or fully discharges (charges into electrical energy). We must use a load to charge a capacitor. The time constant is RC, where C is the capacitance and R is the load resistance of the circuit. The capacitor starts to charge when a power source is placed in its path. When fully charged, it will wait for the appropriate time to release the energy it has accumulated.

Role of capacitor in DC circuit

The capacitor starts to charge as soon as a DC supply is connected since DC sources have continuous voltage. Once fully charged, it will wait for the right time to release the charge it has saved. The outcome is that it is an open circuit after being fully charged. As a result, the capacitor acts as a component of an open circuit. The charge is continually charged and discharged with an alternating current, though, due to the variable voltage. The capacitor, therefore, performs the role of a resistor. In this instance, reactance is used in place of resistance, and a capacitor’s reactance is equal to

$$
\frac{1}{2 \pi f C} .
$$

The function of a capacitor in an AC circuit

Electrical circuits contain capacitors, which store electrical energy and raise the circuit’s power factor.

$$
\text { Power factor }=\frac{\text { Real Power }}{\text { Apparent Power }}
$$

AC through the capacitor (Derivation)

Suppose Q is the charge on the capacitor at a given time t, and the instantaneous voltage is V across the capacitor, then we can write,

$$
V=\frac{Q}{C}
$$

The voltage across the source and the capacitor is uniform. Then, according to Kirchhoff’s loop rule

$$
V=V_m \sin \omega t
$$

From the above two equations, we can write that,

$$
V_m \sin \omega t=\frac{Q}{C}
$$

Again,

$$
I=\frac{d Q}{d t}
$$

$$
I=\frac{d}{d t}\left(C V_m \sin (\omega t)\right)=\omega C V_m \cos (\omega t)
$$

Now, as we know,

$$
\begin{gathered}
\cos (\omega t)=\sin \left(\omega t+\frac{\pi}{2}\right) \\
I=I_m \sin \left(\omega t+\frac{\pi}{2}\right) \\
I_m=\frac{V_m}{\left(\frac{1}{\omega C}\right)}
\end{gathered}
$$

\(\frac{1}{2 \pi f C} \) is the capacitive reactance and is denoted by \(X_C\).

So,

$$
I_m=\frac{V_m}{X_C}
$$

Summary

The capacitor is an electrical part that creates a direct connection with the voltage of the source of alternating current. The capacitor alters its charge or discharge in response to a change in the supply voltage. With no real current travelling through the capacitor, the circuit’s current will first flow in one direction before switching to the other. In a circuit with direct current, things are different. The capacitor plate contains both positive and negative charges when current passes through it when it is linked to a direct current circuit. In many diverse sectors, including energy storage, filters, rectifiers, and other things, capacitors are used. Additionally, it is utilised in circuits to increase voltage and smooth out current swings.

Frequently Asked Questions

1. What is capacitive reactance?

Ans: The capacitive reactance in an electric circuit is the resistance that a capacitor presents to the flow of alternating current

2. State Kirchhoff’s voltage law.

Ans: The algebraic sum of potential differences and electromotive forces is zero in a closed loop.

3. State the role of the capacitor in the AC circuit.

Ans: The charge is continually charged and discharged in an AC circuit due to variable voltage. The capacitor, therefore, performs the role of a resistor. In this case, reactance is used in place of resistance, and a capacitor’s reactance is equal to \(\frac{1}{2 \pi f C} \).

4. State the role of the capacitor in the DC circuit.

Ans: The capacitor starts to charge as soon as a DC supply is connected because a DC source’s voltage is constant. Once fully charged, it will wait for the right time to release the charge it has saved. The outcome is that it is an open circuit after being fully charged. As a result, the capacitor acts as a component of an open circuit.

5. What is an electrolytic capacitor?

Ans: An electrolytic capacitor is a capacitor in which ion mobility makes conduction feasible. A liquid or gel with a high ion concentration is called an electrolyte.

Introduction

All living things require energy to carry out their many tasks, such as breathing, growth, metabolism, and movement. Because of this, cells need a constant flow of energy to support their development, maintenance, and repair. Although the sun is a good source of energy, not all types of life can use it directly. The process by which all the cells in living things produce energy is called cellular respiration. The body receives energy via the breakdown of glucose, whether oxygen is present or not.

What is Aerobic Respiration?

During aerobic respiration, glucose present in the food is converted into water and \(C{O_2}\). It releases energy in the form of ATP (Adenosine triphosphate) and each ATP hydrolysis gives 7.3 kcal/mol. Through this catabolic process, food is converted into energy that is needed for various body functions. Eukaryotes, prokaryotes, and plants undergo this process. The process is also known as oxidative metabolism.

Aerobic Respiration Equation 

When glucose is completely burned, carbon dioxide and water are released with energy as a byproduct. The overall equation of aerobic respiration is given here,

\[{{\bf{C}}_6}{{\bf{H}}_{12}}{{\bf{O}}_6}\left( {{\bf{Glucose}}} \right) + {\bf{6}}{{\bf{O}}_2}({\bf{Oxygen}}){\bf{6C}}{{\bf{O}}_2}\left( {{\bf{Carbon}}{\rm{ }}{\bf{dioxide}}} \right) + {\bf{6}}{{\bf{H}}_2}{\bf{O}}\left( {{\bf{Water}}} \right) + {\bf{Energy}}\]

About 2900 kJ are released and transformed into ATP, which is used for several purposes.

Steps Involved in Aerobic Respiration

The process of aerobic respiration involves four major steps with intermediate reactions. Those are as follows.

Glycolysis

Initially, glycolysis was derived from the Greek words glyco (meaning sugar or sweet) and lysis (meaning dissolution). As a universal sequential reaction, it occurs in both aerobic and anaerobic respiration in the cytosol of a cell.

• Two ATP molecules and two NADH molecules are produced when one glucose (glycogen) molecule breaks down into two molecules of three carbon compounds pyruvates.
• NADH (NAD+H) is the reduced form of NAD (nicotinamide adenine dinucleotide), which is the electron acceptor. The further process of aerobic respiration is carried out by these molecules. 
• Glycolysis is also called the “Embden- Meyerhof-Parnas” (EMP) Pathway.

Pyruvate oxidation (linking reaction)

• During this linking reaction, two stages are connected so that the end product of glycolysis can be used in the citric acid cycle.
• The enzyme pyruvate translocase assists in the entry of the two pyruvate molecules into the mitochondrial matrix. 
• Acetyl-CoA is formed by the oxidation of pyruvate by the Pyruvate dehydrogenase complex.

Citric acid/Krebs cycle

• Citric acid is produced by combining Acetyl-CoA with four-carbon oxaloacetate.
• ATP and carbon dioxide are produced sequentially, along with NADH and FADH reduced forms.
• It is also known as the TCA cycle (tricarboxylic acid cycle) because citric acid has three carboxyl groups.

Electron Transport Chain (ETC)

• This last stage of aerobic respiration occurs in the mitochondria. 
• ETC is a cluster of proteins that transports electrons across a membrane into mitochondria and generates a significant amount of ATP.
• One glucose molecule is broken down into 32 molecules of ATP during this aerobic respiration process.

Examples of Aerobic Respiration

• All multicellular species, including humans, birds, animals, and insects, partake in aerobic respiration. The glucose in the food breaks down in the presence of oxygen and releases energy. 
• It occurs in the majority of higher plants also.

Do all human cells carry out aerobic respiration?

All the cells in the human body are capable of doing aerobic respiration. However, during intense physical activity such as running, jogging, jumping rope, aerobic dance, and cycling up hills, where low oxygen levels result in low energy levels in the body, muscle cells can do anaerobic respiration. To obtain energy, the muscle cells resort to anaerobic respiration.

Aerobic Respiration in Plants

• In the cytosol and mitochondria of plant cells, aerobic respiration takes place.
• Oxygen and simple carbohydrates such as glucose function as reactants. 
• The stomata, which are pores in the epidermis of a plant’s stem and leaves, allow oxygen to enter the plant while it is engaged in aerobic respiration. 
• With the assistance of ambient oxygen, glucose completely breaks down to produce carbon dioxide and water. 
• Additionally, a significant amount of energy is released in the form of ATP.

Significance of Aerobic Respiration

• Living things require ATP that is produced during aerobic respiration to participate in metabolic processes and perform necessary bodily functions.
• Carbon dioxide, the by-product of aerobic respiration, can be used for photosynthesis in green plants. 
• Water, carbon dioxide, and sunlight can be combined during photosynthesis to produce food for plants. 
• Cell division also uses the energy that is generated during respiration.
• The intermediate compounds, organic acids, and coenzymes are useful for organic activities.

Summary

During aerobic respiration, glucose present in the food is converted into water and \(C{O_2}\). When glucose is completely burned, carbon dioxide and water are released as by-products along with energy. The process of aerobic respiration involves four major steps with intermediate reactions. Those are glycolysis, pyruvate oxidation, Krebs’s cycle, and the electron transport chain. In the cytosol and mitochondria of plant cells, aerobic respiration takes place.  Carbon dioxide, the by-product of aerobic respiration, can be used for photosynthesis in green plants.

Frequently Asked Questions

1. Which respiration process transforms glucose into energy more efficiently, and why?
Ans. The 36 ATP molecules are produced by aerobic cell respiration. The efficiency of aerobic cell respiration is about 18 times greater than that of anaerobic cell respiration. Due to the entire conversion of glucose into \(C{O_2}\) and energy, there is a significant amount of energy production.

2. What are ATP and NADH?
Ans. Adenosine triphosphate, or ATP, is an energy-carrying molecule that fuels the metabolism of living things. Nicotinamide adenine dinucleotide, or NAD, is an electron acceptor; its reduced version is called NADH.

3. What is the difference between breathing and cellular respiration?
Ans. While cellular respiration is a process of obtaining energy to carry out various bodily tasks, breathing is a process of exchanging gases between the environment and an organism.

4. Does anaerobic respiration takes place in the human cells?
Ans.  During heavy workouts, anaerobic respiration takes place in the muscles. Since there is no complete breakdown of glucose in anaerobic respiration, the energy liberated is less than that of aerobic respiration. The muscles accumulate lactic acid when you exercise vigorously. Then, this lactic acid oxidizes to produce water and \(C{O_2}\).

5. Where does oxygen-assisted respiration occur within the cell?
Ans. The cytoplasm of the cell serves as the starting point for aerobic respiration, which concludes in the mitochondria. The mitochondria are where the majority of aerobic respiration’s reactions take place.

Introduction

Ray diagrams allow us to ascertain the direction of the light as it moves to a certain location on an image of an item. In the Ray diagram, the incident and reflected rays are shown as lines with arrows. It also helps in determining the path of the light. Spherical mirrors are defined as having painted curved surfaces on one of its sides. Convex mirrors are spherical mirrors with painted inner surfaces, whilst concave mirrors are those with painted outward surfaces.

Representation of Images Formed by Spherical Mirrors Using Ray Diagrams

Ray diagrams may demonstrate how an image is created by tracing the routes taken by the incident and reflected light rays. They are designed in a way that allows each person to focus on a certain area of the object’s depiction. These ray diagrams rely on where the item is.

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Rules for image formation of Spherical Mirror

• After reflection, a ray parallel to the main axis travels through the mirror’s focus.
• A ray that enters the primary focus after being reflected by the surface aligns with the primary axis.
• After reflection from the mirror surface, a light ray passing through the centre of curvature will reflect at a 180^o angle.
• If a light beam is reflected at the mirror’s pole but is not parallel to the primary axis, it will obey the law of reflection.

These are all the above rules for obtaining an image formed by a concave mirror or convex mirror.

Table of image formation by a concave mirror

Sr-no	Position of the object	Position of the image	Image Size	Nature of the Image
1	Between Pole and Focus	Behind the Mirror	Enlarged	Virtual and Erect
2	At Focus	At Infinity	Highly enlarged	Real and Inverted
3	Between Center of Curvature and Focus	Beyond Center of Curvature	Enlarged	Real and Inverted
4	At the Center of Curvature	At the centre of curvature	Same Size	Real and Inverted
5	Beyond Center of Curvature	Between Focus and centre of curvature	Diminished	Real and Inverted
6	Infinity	At the focus	Point size, Highly diminished	Real and Inverted

Ray diagram for Convex Mirror

Image formation by a convex mirror for different positions of the object.

Sr. No.	Position of the object	Position of the image	Image Size	Nature of the Image
1	Between infinity and the pole	Between Pole and focus behind the mirror	Diminished	Virtual and erect
2	Infinity	At focus behind the mirror	Point Size, Highly Diminished	Virtual and erect

Mirror formula

The relationship between the object distance (u), image distance(v), and focal length (f) of the mirror. 

1f=1v+1u

You can read more about Mirror Formula and different types of mirror in this article.

Summary

Ray diagrams are created when we use lines on paper or another flat surface to represent light rays and other rays. Understanding where and what kind of picture will develop is made easier with the aid of the Ray diagram of a spherical mirror. Hospitals, businesses, and other commercial settings often use these mirrors. It will be simple for us to analyse them now that we are aware of the two types of spherical mirrors and their applications regarding how the ray will behave after reflection.

Frequently Asked Questions (FAQs)

1. What is a Ray diagram?

Ans: Ray diagrams show the route travelled by light and what happens when it strikes a surface. In a ray diagram, each ray is represented as follows: a straight arrowhead pointing in the direction of the moving light. A ray diagram is a diagram that depicts the path that light takes to reach a certain location on an object’s image. On the diagram, rays represent the incident and reflected rays (lines with arrows).

2. How do you find out whether a mirror is concave or convex?

Ans: Spherical mirrors have a curved side painted on them. A mirror may be made by splitting a hollow spherical into pieces, painting the exterior, and using the interior as the reflecting surface. Concave mirrors are what these are. The outside of the hollow spherical becomes the reflecting surface if the object is painted from the inside. Convex mirrors are the name for this kind of mirror. Both mirrors serve different functions and provide different picture types.

3. What type of image is formed by concave and convex mirrors?

Ans: The light reflects off an object when it is placed in front of a mirror, creating a real or imagined image of it. When the light beams meet, a real image is created. Virtual pictures are produced when light beams from a point appear to diverge. A plane mirror can only ever generate a virtual image, but a spherical mirror can produce both virtual and real images. A concave mirror will create a real or virtual image. Virtual, upright images can only be reflected in a convex mirror. Depending on where it is placed, the concave mirror can provide an actual or virtual image. No matter where the item is, the convex mirror’s image is only a virtual and upright representation.

Introduction

Viruses are small highly contagious creatures which live on the threshold of life and death. The most distinguishing characteristic of viruses is to multiply inside the living cells of other species. When this virus enters our bodies, it affects our immune systems, hence weakening us. When viruses enter our body they use the host mechanism to carry out their life process, as a result, the host(human) does not get the required energy and becomes weak. Viruses such as HIV majorly infect the cells of the immune system making them more susceptible to various other diseases.

HIV

HIV stands for Human Immunodeficiency Virus and is a small virus which belongs to a group of viruses known as retroviruses. This organism is the cause of AIDS. Human immune cells, also referred to as white blood cells(specifically the Helper T Cells), get infected by HIV, hence compromising the host’s immunity. 

Process of infection of HIV

The HIV infection occurs when the blood of the infected person mixes with the blood of the healthy person. A virus enters the body following is the process of infection.

• When HIV first enters a person’s body, it locates and attaches to CD4 lymphocytes, which are essentially fighting cells  of the immune system.
• The virus attaches and then releases its RNA into the cell.
• The retroviruses then synthesis DNA from RNA by the  enzyme reverse transcriptase.
• The viral DNA fuses with the lymphocyte’s cellular DNA and becomes a part of the genetic makeup of the cell.
• The virus now creates a large number of its own copies using the cell’s replication system, which are then released into the blood to infect additional CD4 cells.

As the body number of CD4 cells in the body decreases due to the infection, the body becomes immunodeficient.

AIDS	HIV
AIDS stands for Acquired Immunodeficiency Syndrome.	HIV stands for Human Immunodeficiency Virus.
AIDS is caused by Human Immunodeficiency Virus.	HIV is a virus that causes diseases.
AIDS is an immunodeficiency syndrome and is the last stage of HIV infection.	The virus infects the immune system and hence compromises the immune system of the host.
Patients show very severe symptoms.	Patients experience minor symptoms during acute and chronic infection stages.
Symptoms include- Breathlessness, lack of strength, swelling in groin regions, getting sick very easily, etc.	Symptoms are- Fever, nausea, body ache, stomach ache, etc.
It is incurable and fatal	Its infection can be controlled to some extent with the help of medicines.

Summary

AIDS is currently quite common disease around the world. This condition is frequently taboo and not discussed in many societies, which unintentionally hastened its rapid global expansion. AIDS and HIV are frequently mistaken for one another, leading to their interchangeability. Despite being closely linked, they are not one and the same. It is important to note that AIDS  is not particularly contagious on its own, which means that it cannot travel quickly through regular channels like air, water, etc. Hugs, sneezes, saliva, sweat, or proximity to infected people do not spread it. 

Frequently Asked Questions

1. Explain detection of AIDS by ELISA Test?
Ans: Enzyme-Linked Immunosorbent Assay,  known as ELISA, is a technique for identifying HIV infection. A  viral protein antigen has already been generated in a laboratory. This antigen is placed in the cassette along with the blood sample of the patient. If the blood has viral antibodies, they attach to the antigen and coagulate hence modifying the look of the cassette’s contents which detects the presences of virus in the blood sample.

2. How is AIDS treated?
Ans: Antiretroviral therapy, generally known as ART, is a form of treatment for AIDS but is not a cure. It has a combination of three distinct drugs. It lengthens the afflicted person’s life span.

3. What distinguishes an antigen from an antibody?
Ans: Foreign chemicals are known as antigens and they have the power to infect the body and cause a disease. Pathogens frequently contain them. 

Immune cells create immunoglobulins called antibodies to fight off particular antigens which are present in the host body cells.

Introduction

The mass of the molecule that may be calculated from the molecular formula is the molecular mass unit. The chemical formula of the molecule’s mass, which indicates the number of atoms in the molecule, is known as the formula unit mass. The formula mass of the chemical formula is calculated using the atomic mass of the element. The formula mass unit is typically used to formulate the mass of ionic compounds, which are compounds made up of ions. It can be challenging to weigh small objects like atoms and molecules that are undetectable to the human eye. However, we have since created mass spectroscopy, which is used to determine the mass of atoms and molecules.

Definition of formula mass

The mass of the chemical compound present is measured in terms of its formula mass unit. The number of moles of the atom present in the compound can be added to determine the formula mass unit. A unit of amu similar to the molecular mass unit exists in the formula mass unit. The molecular mass unit’s calculated mass can be the same as or different from the formula mass unit’s calculated mass. The attraction between molecules has no impact on the mass unit in the formula mass. The empirical formula of the compound determines the formula mass unit.

Unit of formula mass

The Atomic mass unit (amu) or um is the unit used in the formula mass unit (unified mass). The atomic mass unit can be defined as the mass of the twelfth part of the Carbon having atomic mass 12. 

Since hydrogen has an atomic mass of one, it was once used as a standard to determine the mass of other multielectron atoms. Due to the abundance of carbon atoms in the environment, however, the carbon atom with atomic mass 12 is usually used to refer to atomic mass.

Formula mass unit of ionic compounds

Formula mass units can be formulated by the addition of the mass of the number of moles of the atom present in the compound. The formula mass unit is based upon the empirical formula of the compound. By adding the mass of the number of moles of the atom present in the compound, formula mass units can be calculated. By adding the mass of the number of moles of the atom present in the compound, the molecular mass units can be calculated the empirical formula of the chemical serves as the base for the mass unit formula.

A huge number of both positively and negatively charged ions are linked together to form an ionic compound. For example, Magnesium oxide is an ionic compound made up of many Magnesium ions \(M{g^{2 + }}\), and Oxygen ions, \({O^{2 – }}\).

For example,

1. Find out the formula mass unit of the ionic compound, such as potassium carbonate \({{\bf{K}}_{\bf{2}}}{\bf{C}}{{\bf{O}}_{\bf{3}}}\).

The formula mass of \({K_2}C{O_3}\) = Mass of 2 potassium atoms + Mass of one Carbon atom + Mass of 3 Oxygen atoms

=2 39+12+3 × 16

=78+12 +48

= 138 u

Thus, the formula mass of potassium carbonate is 138 u.

2. Calculate the formula unit mass of \({\bf{Ca}}{({\bf{OH}})_{\bf{2}}}\).

The Formula mass of \(Ca{\left( {OH} \right)_2}\), = mass of calcium atom + 2 (mass of oxygen atom+mass of the hydrogen atom)

= 40+2(16+1) 

= 74 u

The formula unit mass of Calcium Hydroxide is 74 u.

Practical Applications of Formula Unit Mass

Stoichiometry and balanced equations

Stoichiometry and balanced equations Formula unit mass is essential for solving stoichiometry problems, allowing chemists to convert between the mass of a substance and the number of formula units. Understanding formula unit mass helps balance chemical equations and predict the amount of products formed or reactants consumed.

Determining empirical formulas

Determining empirical formulas Empirical formulas represent the simplest whole-number ratio of elements in a compound. By calculating the formula unit mass and using the mass percentages of each element, chemists can determine the empirical formula of a compound, which is crucial for understanding its chemical properties.

Calculating percent composition

Calculating percent composition Percent composition expresses the percentage of each element in a compound by mass. Using the formula unit mass and the atomic masses of the constituent elements, chemists can calculate the mass percentage of each element in a compound, allowing for deeper analysis and comparison of substances.

Analyzing chemical reactions and compounds

Analyzing chemical reactions and compounds Understanding formula unit mass enables chemists to explore the properties of ionic compounds and their reactions. Knowledge of formula unit mass assists in predicting reaction outcomes, determining limiting reactants, and identifying unknown compounds in analytical chemistry.

Summary

The term “formula unit” refers to the simplest possible ion arrangement that results in an electrically neutral unit in an ionic compound. Atomic mass units serve as the basis for the formula mass unit. The formula mass unit is the mass of the completed chemical formula, whereas the molecular mass unit is the mass of the molecular mass. By adding the atomic mass of the number of moles of the atom present in the formula, the formula unit mass may be calculated.

Frequently Asked Questions

1. What do you mean when you refer to an atomic mass unit?

Ans. A unit of atomic mass is defined as the mass of 12 parts of carbon, which has an atomic mass of 12. The abbreviation for the atomic mass unit is amu or um (unit mass).

2. What is the difference between molecular mass and formula mass of elements?

Ans. The molecular mass unit depends on the attractive force such as that which forms dimers or trimers, whereas the formula mass depends on the number of moles of atoms involved and not on the attractive force involved in forming dimers or trimers.

3. What is the formula unit mass? Give example.

Ans. The total atomic masses of the constituent elements of a compound are used to define the formula mass of a substance. This is typically applied to compounds that are made up of ions rather than separate molecules. For example, Sodium and chlorine ions are used to form NaCl (sodium chloride).

The formula mass of NaCl= Mass of 1 Sodium atom+ Mass of one Chlorine atom

=1 × 23+1 × 35.5

= 58.5 amu

Thus, the formula mass of NaCl is 58.5 amu

An Introduction to Molecules of Compounds

A molecule is a group of two or more atoms held together by chemical bonds, which are attractive forces. Molecules are the smallest particles of a substance that possess all of its physical and chemical properties. Many thousands of atoms make up biological molecules like protein and DNA. A compound is a molecule composed of atoms from various chemical elements. Compounds are divided into two types: molecular compounds and ionic compounds. They can only be broken down chemically. Compounds are made up of a fixed number of atoms held together by chemical bonds.

Compounds are homogeneous in nature and cannot be physically separated.

What are Molecules of Compound

A compound molecule is a combination of two or more atoms of different types. This means that molecules of compounds contain atoms from two or more different chemical elements, such as methane, water, carbon dioxide, ammonia, and so on. We can further categorize them based on the number of atoms in the molecule. The chemical bonding between the atoms can be either covalent or ionic.

Ionic bonds are always formed between molecules containing cations (positive ions) and anions (negative ions). As a result, an ionic compound is always formed between two different chemical elements. Covalent bonds are formed when two atoms share electrons equally.

What are the types of Elements?

1. Metals-They are substances with properties such as malleability, ductility, sonority, electrical and thermal conductivity, lustre, and solidity. Metals have extremely high melting points. The majority of pure metals are found in the earth’s crust. They are found in ores, which are solids. Zinc, iron, copper, aluminium, lead, chromium, cadmium, nickel, tin, zinc, and so on.
2. Non-Metals– They are substances that are neither malleable nor ductile and do not conduct heat or electricity. Carbon, sulphur, phosphorus, silicon, oxygen, and other elements are examples.
3. Metalloids– A chemical element with properties of both metals and non-metals. Metalloids have properties that fall somewhere between metals and non-metals. For example, arsenic, silicon, boron, and so on.

What are the types of Compounds?

1. Molecular Compounds-Molecules are compounds that can be formed by the combination of the same or different atoms. The atoms are joined to form a definite shape that is defined by the angles between the bonds and the lengths of the bonds. Carbon dioxide, water, ammonia, and other gases are examples.
2. Ionic Compounds- It is made up of both positive and negative ions. When dissolved in water, they completely decompose into ions. Examples include sodium chloride (NaCl), potassium chloride (KCl), copper sulphate (\(CuS{O_4}\)), and others.

Summary

When two or more elements combine chemically in a fixed mass ratio, the resulting product is known as a compound. Compounds are substances made up of two or more different types of elements in a fixed ratio of their atoms. When the elements combine, some of their individual properties are lost, and the newly formed compound has new properties.

Frequently Asked Questions

1. How do molecules form?

Ans: When atoms come close together, their electron clouds interact with one another. Other, as well as with nuclei If the energy of the system decreases as a result of the interaction, the atoms bond together to form a molecule.

2. What do you understand by molecules of compounds?

Ans: A molecule is a general term for any atoms that are linked together by chemical bonds. A molecule is any atom combination. A compound is a molecule composed of atoms from various elements. Not all molecules are compounds, but all compounds are molecules.

3. What are the types of Molecules of Compounds?

Ans: There are two types of compounds: molecular compounds and Ionic compounds. Atoms in molecular compounds are held together by covalent bonds. It is held together in salts by ionic bonds. These are the two types of bonds that every compound is composed of.

An introduction to Molecules

Atoms are the building blocks of all living things on this planet. An atom is the smallest unit that makes up a chemical element. Atoms make up everything else that is solid, liquid, or gas. Atoms are made up of protons, neutrons, and electrons that are contained within the nucleus of an atom. What happens when two or more atoms collide? They combine to form molecules. Molecules are formed when two or more atoms form chemical bonds with one another. Understanding the properties and structure of atoms and molecules is not easy, but once understood, it is a fascinating subject to study.

What are Molecules?

Elements are created when the same types of atoms combine. The number of atoms that make up a molecule has the same ratio. The structure of elements determines their properties. Elements can be made up of one or more atoms. Take, for example, oxygen, which has two atoms (\({O_2}\)). Atoms are not depicted to scale. A compound is formed when these elements are combined. We can use \({H_2}O\) in this case. Water contains two hydrogen atoms and one oxygen atom. Similarly, larger chemical compounds such as methane (\(C{H_4}\)). We can learn from these how a group of atoms with a nucleus can form elements and compounds with various properties and structures.

What is the difference between Atoms and Molecules?

Atoms	Molecules
Atoms are the smallest particle that can exist.	Two or more atoms combined to form molecules.
Atoms may not be stable due to the presence of electrons in the outer shells.	Molecules attain stability.
They contain protons, neutrons, and electrons.	Two or more atoms are formed and hence, they are strong.
Examples: Oxygen (O), phosphorus (P), sulphur (S) etc.	Examples: Oxygen (O2), water (H2O), and sulphur (S8).

Summary

Elements can be single atoms, such as He, or elemental molecules, such as hydrogen (\({H_2}\)), oxygen (\({O_2}\)), chlorine (\(C{l_2}\)), ozone (\({O_3}\)), and sulphur (\({S_8}\)). Atoms are not depicted to scale. Some elements are monatomic, which means that their molecular form is made up of a single (mono-) atom (-atomic).

Frequently Asked Questions (FAQs)

1. What do you understand by the Law of Conservation of Mass?

Ans: According to this law, “Mass can neither be created nor destroyed.” This law can be applied to a chemical reaction in the following way:- During a chemical reaction, the total mass of reactants equals the total mass of products.

\[\left( {Reactant} \right){\rm{ }}A + B{\rm{ }} \to {\rm{ }}AB{\rm{ }}\left( {Product} \right)\]

2. What is an atom?

Ans. According to modern atomic theory, an atom is the smallest particle of an element that participates in a chemical reaction and retains its identity throughout the chemical or physical change.

3. What do you understand by the Law of Constant Proportion?

Ans. According to this law, “A pure chemical compound always contains the same elements combined in the same proportion by mass, irrespective of the fact from where the sample has been taken or from which procedure has it been produced.”

Introduction

The essential building blocks of living things are cells. There are billions of cells that make up the human body. A group of specialized cells which perform one or more similar functions are referred to as a tissue. They combine to produce several organs, such as the skin, kidney, lungs, liver, and heart. An organ system is made up of two or more organs that perform the same tasks. Each of these contributes to the overall body’s survival.

Types of animal tissues

Animal tissues are classified into four kinds based on their origins, structures, and functions. Animal tissues are of the following types-

• Muscular tissues
• Nervous tissues
• Epithelial tissues
• Connective tissues

Muscular tissue

Muscular tissue, which is considerably longer and has the ability to contract and expand, which causes motion. These tissues have a lot of blood vessels since they help in activities like running, walking, swimming etc.

Features of Muscular tissues

• Muscular tissues contract in response to stimuli to produce motion.
• They can be stretched more than their length.
• These tissues are elastic in nature because they can expand and then contract to their original length.
• They can adapt to their surroundings.

Types of Muscular Tissues

Types	Location	Function
Cardiac muscle	Heart	Continuous blood pumping
Skeletal muscle	Skeletal bone	Movement
Smooth muscle	Eyes, uterus, blood vessels, and digestive tract	Maintain blood flow and blood pressure

Nervous tissues

Nervous tissues make up the central nervous system (CNS) and peripheral nervous system (PNS). By sending nerve impulses, the neural or nervous tissue is in charge of control and coordination of  numerous bodily functions. The spinal cord, the brain, and the nerves are part of nervous system and that stimulate muscle contraction and regulate emotions, memory, and reasoning.

Neurons

Axon, dendrites, and cell bodies make up a neuron, and they are responsible for transmitting and receiving signals throughout the body.

Types of neurons– According to their functions, neurons can be divided into the following types:

• Sensory neurons– Short axons and lengthy dendrites are characteristics of unipolar sensory neurons. They are also referred to as afferent neurons since they transport action potential from the sensory receptor to the CNS and brain.
• Motor neurons– Motor neurons are multipolar and operate as efferent neurons because they transport the action potential from the central nervous system to activate muscles.
• Associated neurons-Associated neurons help the brain learn, make decisions, and regenerate new neurons. They are multipolar neurons which connect sensory and motor neurons.

Neuroglial cells 

It is responsible for supporting and maintaining the nervous system and they are of following types-Astrocytes, Ependymal cells, Microglial cells, Oligodendrocytes, Satellite cells and Schwann cells.

Epithelial tissues

All of the body’s inner and outer surfaces are lined and covered with epithelial tissue. The cells form single or several layers and are tightly packed together.

Features of Epithelial Tissues

• Without intercellular gaps, cells are tightly grouped together to form a sheet.
• Gap junctions, tight junctions, and adherent’s junctions connect the cells.
• Despite being non-vascular, or lacking a blood supply, these are innervated (supply nerves to organs or parts of the body).
• These tissues regenerate rapidly.
• Although they lack a blood supply, they receive nutrition from substances that diffuse from the blood vessels of the underlying tissues.
• At the basal surfaces, the epithelial tissues are joined to the connective tissues to forming  basal membranes.
  Types of Epithelial Tissues

Types	Location	Function
Simple squamous	Blood vessels, capillary walls, air sacs, linings of lymph	Transport the selective material to pass through osmosis, diffusion, filtration, and absorption
Simple cuboidal	Lining of ducts, tubular linings of kidneys, surfaces of ovary	Absorption and secretion
Simple columnar	Linings of the respiratory tract, digestive tract and uterus	Mucous secretion, absorption and protection
Transitional epithelium	Inner linings of the ureter, urethra and urinary bladder	Prevent reabsorption of toxic materials
Pseudostratified columnar	Linings of respiratory passage	Secretion, movement of mucous and protection
Stratified squamous	Throat, linings of the mouth, vagina, and the outer surface of skin	Protection
Stratified cuboidal	Salivary glands, mammary glands, pancreas and sweat glands	Protection
Stratified columnar	Parts of the pharynx and male urethra	Secretion and protection

Connective tissues
Connective tissues connects and supports the body’s all the other tissues and organs. These tissues have the capacity to store fat and aid in the flow of nutrients and other substances between the tissues and organs throughout the body. This transport of nutrients is done thorough the process of diffusion.

Features of Connective tissues

• Extracellular matrix and cells make up the connective tissue.
• Mast cells, macrophages, plasma cells, adipocytes, chondrocytes, fibroblasts, osteoblasts, and osteocytes are the cells that present in the connective tissue.
• Extracellular matrix is made up of tissue fiber and the ground substance.
• Collagen, elastic, reticular, and fibrillin are the tissue fibers present in the connective tissue. Glycoproteins, glycosaminoglycans, and proteoglycans are ground substances present in the connective tissue.
  Types of Connective tissues

Types	Location	Function
Non-fibrous connective tissues- Blood and adipose tissue.	Blood was found throughout the body. Adipose tissue found in association with areolar tissue.	Provides nutrition and oxygen to the body. Adipose tissue is a good insulator and source energy reserve.
Collagen fibers	Tendon, Ligament, Skin, Cartilage, Bone etc.	Binding bones and other tissues
Elastic fibers	Extracellular matrix	Give elasticity to the organs and helps to retain original position post stretching.

Summary

Animal tissues are categorized according to their shape and function. Tissues are groups of cells having similar functions. Epithelial tissue is present on the upper skin surfaces which have intercellular substances and densely packed cells. Epithelial tissues include squamous, cuboidal, columnar, stratified, transitional, and pseudostratified tissue types. Muscle tissues can contract the muscles to perform particular functions in the heart, skeleton, blood vessels, eyes, and digestive tract. Connective tissues support the placement of organs to enable optimal internal organ form and function. It consists of adipose, areolar, blood, lymph, tendon, ligament, cartilage, bone, and lymphatic tissues. Nervous tissue contains neurons and neuroglial cells that are present  in the brain and spinal cord to control the CNS and PNS and helps entire bodily control and coordination.

Frequently Asked Questions

1. How are various tissues derived?
Ans: All tissues come from one of three distinct germ layers. During embryonic development, these germ layers are formed. They are as follows-

• The epidermis and nervous system are formed from the ectoderm (outer layer).
• The middle layer, or mesoderm, eventually forms connective tissue and lines the body’s cavities.
• The inner layer, or endoderm, gives rise to a number of internal organs, including the pancreas and liver, as well as the lining of the digestive tract, respiratory system, and reproductive system.

2. Give the classification of neurons based on their structure.
Ans: Based on their structural characteristics, neurons can be divided into the following types:

• Bipolar neurons- Axons and dendrites are two of the extensions seen on bipolar neurons.
• Unipolar neurons- There is only one extension from the body of a unipolar neuron (one axon).
• Multipolar neurons- One axon and several dendrites characterize multipolar neurons.

3. What are bones?
Ans: Bones are connective tissue with abundant collagen and calcium, they provide support for the joints that make up the skeletal system of the body. These are places where various lymphocytes of the immune system develop and help in protection of the body.