Category: Physics Notes PPT

Hydrosphere is the part of the earth where water exists in forms of surface water, underground water and in the air. Approximately, 71% of earth that is 361740000 square kilometers is surrounded by water. Oceans, lakes, rivers, underground water, streams, ice lands and water vapour in the atmosphere are collectively called the hydrosphere. 

 

The existence of hydrosphere depends on an important phenomenon called the water cycle or the hydrological cycle. There are four steps in the Water cycle. Those are evaporation, condensation, precipitation and surface run-off. Water from lakes, oceans, streams, etc. evaporates by the sun’s heat. This transformation of state from liquid to gas is called evaporation. Water vapour carried away by hot air starts to cool when it goes higher from the earth’s surface. Later it transforms in the form of clouds. 

 

This process is known as condensation. When the water accumulates in the clouds, it becomes heavy and starts to fall back in the form of snow or rain depending upon the temperature of the atmosphere. This process is known as precipitation. When it rains, a small quantity of water is absorbed by the soil and becomes groundwater. The remaining part flows through the hills, mountains and is collected in different parts of the hydrosphere. This process is termed as surface run-off. This cycle of water passing different states and stages is called the hydrosphere.

Importance of Hydrosphere

As we all know, the survival of living organisms without water is impossible. Life on the earth entirely depends upon water. Hence earth is known as a water planet. Hydrosphere plays a vital role in our daily life. A few importance of hydrosphere are as follows: 

 

1. One of the Basic Needs of Human

Apart from drinking, water is essential for cooking, cleaning, washing and even for the functioning of so many industries. In addition to this, water is necessary for agriculture and the generation of electricity through hydropower. It is difficult to imagine a day without water. 

 

2. Part of a Living Cell

The main component in the cells of all living organisms is water. It is found that 75% of the cell is composed of water. Most of the chemical reactions occurring in the cells are mainly due to the presence of water. Survival of a cell is impossible without water. In plants, the energy transportation is done with the help of these water molecules only.

 

3. Habitat for Many Organisms

Hydrosphere is the habitat for numerous aquatic plants and animals. The number of living organisms in water is high when compared to the number of organisms that are living on land. Plants and animals in the water make use of gases such as oxygen and carbon dioxide that are dissolved in water for their existence. They also use nutrients such as ammonium ions, nitrate, etc. for their life.

 

4. Regulates Temperature

One of the important features of the hydrosphere is that it helps to regulate the temperature of the environment. The specific heat capacity of water is the main property by which this regulation is happening. Water takes time to heat as well as to cool. So the places surrounded by water bodies like oceans and lakes tend to have a balanced climate. The temperature in the coastal areas may not have extreme temperature differences. Not only maintains atmosphere temperature, but also regulates temperature for all living organisms. 

 

5. Atmosphere Existence

Hydrosphere plays an important role in the present form of atmosphere. Above 400 million years ago, the earth’s atmosphere was covered with helium and hydrogen. Earth’s atmosphere was very thin and was similar to the planet Mercury’s present atmosphere and the temperature was around 600°C. Later on, when the earth’s surface cooled and as a result of so many chemical reactions, the water bodies and atmosphere formed in massive amounts.

 

How do Human Activities Affect the Hydrosphere?

Irresponsible human activities are the main cause of the depletion of water sources and pollution of the hydrosphere. Cutting down of trees badly affects the environment and causes global warming. These adverse changes affect the natural hydrological cycle. Discharge of waste from the industries, toxic chemicals, pesticides, radioactive substances and plastics into the water bodies have a bad impact on the freshwater system as well as the aquatic plants and animals. The burning of fossil fuels is the major source of emission of harmful greenhouse gases such as carbon dioxide, sulphur dioxide and nitrogen oxides. These gases cause acid rains. When this water is collected in the hydrosphere, the water becomes acidified and this has become a big problem throughout the world. Most of the fishes cannot survive in the acidified water and gradually their population started to decrease. 

 

The increase in population will increase the need for water. But our lakes, rivers, freshwater ponds and wells are disappearing. The scarcity of fresh water is going to become a serious problem in the upcoming years. Due to the rise in temperature, now it is a challenge to sustain the hydrosphere. 

 

How to Save the Hydrosphere?

The existence of a hydrosphere is essential for the existence of life in the world. We can take small steps to conserve water through which we can sustain our water bodies. It seems to be simple. But as a whole, drastic changes can be made. 

1. Try to grow native plants that are adapted to the climate of the locality. They may not require much water and fertilisers.

2. Dispose of toxic chemical substances like paint, bottles of medicines, plastics and other hazardous materials properly. Don’t throw it into the water bodies.

3. Avoid tiling the foreground in front of the house. By doing so, the rainwater may not trap in the soil and this will lead to the reduction of groundwater in the surroundings.

4. Protect the ponds and wells by not throwing trash into them.

5. Nowadays water-conserving models of sanitary items are available in the market. Try to choose those kinds of models.

6. Make sure there is no leakage in the toilets and household taps.

7. Wash the vegetables, clothes and motor vehicles by using a limited amount of water.

8. Use environment-friendly products like lime juice, vinegar, etc. for washing utensils. This type of product may not harm the environment and the water bodies.

9. Oceans are the main sources of water. When you are going for a picnic on beaches, do not throw any plastic bottles or waste products into the water.

10. Educate the children about the importance of water and teach them the methods to save our hydrosphere from today onwards. Small changes that start from each house lead to a big effect which results in retaining the beauty of the environm
    ent.

11. An oil spill is also one of the main reasons why the hydrosphere gets affected. Because the dispersion of oil over the surface of the water forms a thin layer that affects the evaporation process. In a way, the hydrosphere gets affected drastically.

Thus, it is our duty to save our land and water from getting affected by chemical hazards and abuse of water bodies. Industrial waste and human waste are the main problems affecting our hydrosphere. By knowing the importance of this, we should take care of this without any fail.

In Newtonian mechanics, equations of motion describe the behavior of a physical system in terms of its motion as a function of time. More particularly, the equations of motion describe the attribute of a physical system as a set of mathematical functions in terms of dynamic variables. However, these variables are spatial coordinates and time that may include momentum components as well. 

Equations of motions are mathematical formulas that describe the position, velocity, or acceleration of a body relative to a given frame of reference.

If the position of an object changes with respect to a reference point then it is said to be in motion w.r.t. that reference while if it does not change then it is at rest w.r.t. that reference point. For a better understanding or to deal with the different situations of rest and motion, we derive some standard equations relating terms distance, displacement, speed, velocity, and acceleration of the body by the equation called equations of motion.

Three Equations of Motion

In the case of motion with uniform or constant acceleration (one with equal change in velocity in equal interval of time), we derive three standard equations of motion which are also known as the laws of constant acceleration. These equations contain quantities displacement(s), velocity (initial and final), time(t), and acceleration(a) that govern the motion of a particle. These equations can only be applied when the acceleration of a body is constant and motion is a straight line. The three equations are,

v = u + at

v² = u² + 2as

$S=ut+frac{1}{2}at^2$

Where, 

s = The total displacement

u = Initial velocity 

v = Final velocity

a = Acceleration 

t = Time of motion 

Derivation of Equation of Motions

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Now let’s start the derivation with one of the simple equations of motion i.e., v=u+at where u is the initial velocity, v is the final velocity and a is the constant acceleration.

Assuming that a body started with initial velocity “u” and after time t it acquires final velocity v due to uniform acceleration a. 

We know that the acceleration of a moving particle is defined as the rate of change of velocity, also which is given by the slope of the velocity-time graph.

Therefore, according to the definition of acceleration and the v-t graph we get,

$Rightarrow text {Acceleration}=frac{text{Change in velocity}}{text{Total time taken}}$

$Rightarrow text {a}=frac{text{(Final velocity)-(Initial velocity)}}{t}$

$Rightarrow text {a}=frac{text{(v)-(u)}}{t}$

On simplifying the above equation we get:

=v=u+at

Now to derive the second equation again suppose a body is moving with initial velocity u after time t its velocity becomes v. The displacement covered by them during this interval of time is S and the acceleration of the body is represented by a.

Explanation: We know the area under the velocity-time graph gives the total displacement of the body. Thus area under the velocity-time graph is the area of trapezium OABC.

Also area of trapezium = $frac{1}{2}(text{sum of parallel sides})times(text{Height})$

Sum of parallel sides = OA + BC = u + v and here, height = time interval t

Thus,area of trapezium =  $frac{1}{2}(text{u})times(text{v})t$

Substituting v=u+at from the first equation of motion we get,

Displacement =S =area of trapezium = [frac {1}{2}] (u + {u + at}) t

S= [frac {1}{2}] (2u + at)t = ut + [frac {1}{2}] at²

This is called the second equation of motion and is the relation between displacement S, initial velocity u, time interval t, and acceleration ‘a’ of the particle.

Now in order to derive the third equation again use 

Displacement = S =area of trapezium = [frac {1}{2}] (u + v) x t

From first equation v=u+at we get v – u= at [frac {v-u}{a} = t]

Substituting the value of t in S = [frac {1}{2}] (u+v) xt

We  get S =
[frac {1}{2}] (u+v){[frac {v-u}{a}]}= [frac {v^2 – u^2}{2a}]

⇒ 2as = v²– u²

⇒ v² = u² + 2as

Which is the third equation of motion and is the relation between final velocity v, initial velocity u, constant acceleration a, and displacement S of the particle.

We can now also calculate the displacement of particles during the nth second, using these equations of motion derived above. 

Displacement for the nth second can be calculated by using the formula given below:

sn= u +
[frac {1}{2}]  a(2n-1)

This equation is often regarded as a modified form of the second equation of motion

The SI unit used to measure distance or length is known as Kilometre. These km units are used in metric systems. The distance between two points can also be measured in other terms like miles, yards, etc. Even though we have many methods to measure distance, the International System of Units created certain limits and denominations to measure distances or length and one of them is kilometre. 

This article described the definition of kilometres, kilometre measurement and the difference and conversions of miles, metres, centimetres, feet and millimetres into kilometres.

 

Definition of Kilometre

A kilometre is an SI unit used for measuring the distance or time. It is a unit of the metric system. A kilometre is usually expressed as km. The international system of units prescribed this unit to follow around the world. So, that all the people around the world are using the same measuring systems and standards for calculating the length of the object or distance between two places.

Conversions Regarding Kilometre Measurements

Kilometres and Miles

The kilometre km is the SI unit used to express the distance. The international standard units announced this km unit. The United States was following the measuring unit called miles to measure distance. It was proposed through “United States Customary Units (USCS)”. Even though both the kilometre and miles are representing the unit of distance. The value of 1 mile is not equal to 1 kilometre.  Here, 1 mile is equal to 1.60934 km.  The term miles are often used in the field of science, medicine and military forces. It is possible to convert USCS units into SI units. 

Kilometre to Meters

Many may have questions that 1 kilometre is equal to how many metres?  One kilometre is equal to 1,000 metres. The metre is also a SI unit of distance. The metre can be expressed in terms of m.  To convert metre into kilometre, a metre value should be divided by 1,000 or multiplied by 0.001. 

For example, 

2m = 0.002km. 

5km = 5,000 m

Kilometer to Centimeters

A centimetre is less than a metre. The centimetre is expressed in terms of cm. 100 centimetres together form one metre. Further, 1,000 metres together form 1 kilometre. So, 1,00,000 cm together is known as 1 km.

For example, 

2 cm = 0.00002 km. 

8 km = 8,00,000 cm

Kilometer to Millimeters

The millimetre is less than the centimetre. The millimetre is expressed in terms of mm.  Here, 1 centimetre (cm) is equal to 10 millimetres.  So, 10,00,000 mm combines together to form one kilometre. 

For example, 

3 mm = 0.000003 km. 

9 km = 90,00,000 mm

Kilometer to Miles

Miles is the important term used to indicate the distance between two places using the USCS unit.  Miles can be abbreviated as ‘mi’.  Here, 1 mile(mi) is equal to 1.60934km. 

Kilometer to Feet

Feet is the important term used to measure the length of the object. This is mainly used in USCS.  Here, 1 km is equal to 3,280.84 ft.

How to Convert Kilometre Per Hour into Metre Per Second? 

The kilometre per hour is the unit to measure the speed of an object which can be calculated by taking the count of distance travelled by the object with the time taken to cover a certain distance.    

1 kilometre per hour =  1,000(meters) / 3,600(seconds) 

Which means, 

1 km/hr= 5/ 18 m/s 

This article explained what is a kilometre, how to convert a metre into kilometre, centimetre, millimetre into a kilometre in detail.

Thermodynamics refers to the study of the transfer of energy that occurs in molecules or collections of molecules. When we are discussing thermodynamics, the particular item or collection of items that we’re interested in is called the system, while everything that’s not included in the system we have defined is called the surroundings. 

For instance, if you were heating a pot of water on the stove, the system might include the stove, pot, and water, while the environment would be everything else: the universe, galaxy, planet, country, neighbourhood, house, and rest of the kitchen. The system and therefore the surroundings together structure the universe. Let us define what an open system is.

About Thermodynamics

Thermodynamics deals with concepts such as heat and temperature, as well as the transfer of heat and other forms of energy.

The four laws of thermodynamics, which offer a quantitative description, regulate the behaviour of these values. William Thomson originated the term thermodynamics in 1

It goes through how thermal energy is converted into and out of different forms of energy, as well as how this impacts matter.

Thermal energy is the energy that is derived from heat. Heat is generated by the movement of small particles within an item, and the faster these particles move, the more heat is generated.

Thermodynamics is not concerned with how quickly these energy transformations occur. It is based on the changing states’ initial and final states. 

It’s also important to remember that thermodynamics is a macroscopic subject. This means it’s more interested in the whole system than in the molecular structure of things.

Thermodynamic System

A thermodynamic system is a physical entity with a defined boundary on which we focus our attention. The system border can be real or imagined, and it can be fixed or flexible.

There are three sorts of systems in thermodynamics: open, closed, and isolated.

• Isolated System – No exchange of energy or mass between an isolated system and its surroundings. The universe is a solitary system. A perfect isolated system is tough to return by, but an insulated drink cooler with a lid is conceptually almost like a real isolated system. The items inside can exchange energy with one another, which is why the drinks get cold, and therefore the ice melts a touch, but they exchange little or no energy with the outside environment.

• Closed System – Within a closed system, energy is transferred but not mass. Closed systems include refrigerators and piston-cylinder assemblies. example, if we put a very tightly fitting lid on the pot, it would approximate a closed system.

• Open System – In an open system, both mass and energy can be transmitted. An open system can exchange both matter and energy that is present with its surroundings. Steam turbines and the stovetop example would be an open system because heat and water vapour are often lost to the air. 

Open System in Thermodynamics – Explanation

An open system may be a system that has external interactions. Such interactions can take the shape of data, energy, or material transfers into or out of the system boundary, counting on the discipline which defines the concept.

In contrast to closed systems, the majority of genuine thermodynamic systems are open systems that exchange heat and work with their surroundings. 

As they grow and develop, living systems, for example, are definitely capable of attaining a local reduction in entropy. They construct structures with greater internal energy (i.e., lower entropy) from the nutrients they take. 

The matter is easily exchanged between the open system and its surroundings. This can be described simply by adding or subtracting matter. 

Energy exchange, on the other hand, can be a little more complicated because energy is frequently transmitted in multiple forms and different transformations might occur throughout this process. Heat or another sort of energy is exchanged.

The energy exchange is defined in thermodynamic terms as:

• Potential Energy

• Kinetic Energy

• Thermal energy

Potential energy is stored energy. Kinetic energy is the energy-carrying by an object while moving. However, the energy of a system always exists in one of these three states or in two states at an equivalent time. For example, a stationary object can exchange heat with the encompassing. Then it’s both P.E. and thermal energy. Energy is often exchanged or transferred as P.E. or K.E. But sometimes, P.E is often converted into K.E or the other can occur. Thermal energy or heat is additionally exchanged between open systems and their surroundings.

For an example of an open system in thermodynamics, the earth can be recognized as an open system. In this case, the world is the system and space is the surrounding. Sunlight can reach the world’s surface and we can send rockets to space. Sunlight and rockets are often explained as energy and matter, respectively.

Due to the potential of exchanging matter between an open system and surrounding, the interior mass of an open system varies with time. If the matter is added, then an increase in the mass can be found and if the matter is removed, then The first decrease in the mass is found.

The first law of thermodynamics considers the big picture. It discusses the overall amount of energy in the universe and, more importantly, it states that this total amount does not fluctuate. Let’s dig deeper into the First Law of Thermodynamics.

First Law of Thermodynamics For an Open System

The first law of thermodynamics is big: It deals with the entire amount of energy within the universe, and it states that this total amount doesn’t change. Put differently, the primary Law of Thermodynamics states that energy can’t be created or destroyed. It can only change shape or be transferred from one object to a different one.

This law could seem quite abstract, but if we start to see examples, we’ll find that transfers and transformations of energy happen around us all the time. 

For Example:

Light bulbs convert electricity into light energy (radiant energy).

One ball hits another, transferring K.E. and making the second ball move.

Plants convert the energy of sunlight (radiant energy) into energy stored in organic molecules.

Importantly, none of these transfers is completely efficient. Instead, in each scenario, a number of the starting energy is released as thermal energy. When it’s moving from one object to another, thermal energy is named by the more familiar name of warmth. It’s obvious that glowing light bulbs generate heat additionally to light, but moving pool balls do too, as do the inefficient energy transfers of plant and animal metabolism. To see why this heat generation is vital, stay tuned for the Second Law of Thermodynamics.

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Difference Between the Open System and Clo
sed System in Thermodynamics

Conclusion

The interactions between systems and their surroundings can be found everywhere in the environment. Systems can be divided into opened, closed, or isolated systems. The main difference between open and closed systems is that in the case of an open system, matter can be exchanged with the surroundings whereas, in the case of a closed system, matter cannot be exchanged with the surroundings.

Conservation refers to the condition where there is no change. So, The variable in an equation, which represents a conserved quantity, is constant over time. Its value remains constant both before and after a particular event.

 

There are many such conserved quantities in physics. They help in making predictions and making a lot of complicated situations much easier. The three fundamental quantities which are conserved in mechanics are energy, momentum, and angular momentum.

 

Though energy changes, it still remains conservative in nature. This is because while referring to energy, it is the total energy of a system that is considered. The movement of objects and external factors change one form of energy into another but essentially, energy is not lost anywhere. But, it should be noted that the theory of conservation of energy should only be applied to isolated systems.

 

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This is why a ball rolling across a rough floor is considered not to obey the law of conservation of energy because it is not isolated from the floor. The floor is doing work on the ball through friction, causing changes in the whole system. 

 

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However, the ball and floor together form an isolated system and thereby the law of conservation can be applied and it has been proved that it holds true in the combined ball-floor system.

 

What do we Mean by a System?

The system can be considered as the suffix we give to a collection of objects. These objects are modeled by the many standard equations. When we describe the motion of an object using the theory of conservation of energy, then the system is supposed to include the object of interest and all other objects that it interacts with.

 

But, it should be noted that in practice, some of these interactions have to be ignored and omitted in order to solve problems or make predictions. The system we define has objects and interactions that are of importance to us. We generally concentrate only on them and only they are included. ‘Environment’ is the term used to call the things we don’t include. While this creates an overall inaccuracy, it is considered negligible. One of the qualities that a good physicist should possess is the common sense and ability required to differentiate what should be included in the environment. 

 

For example, 

 

When we consider a problem involving a person bungee jumping from a bridge. At the very minimum, the system should consist of the jumper, bungee, and the Earth. If a more precise calculation should be done, one should include the air, which does work on the jumper via drag, or air resistance. To increase the accuracy, one can include the bridge and its foundation, but the bridge is obviously much heavier than the jumper, hence it can be included in the ‘environment’.

 

What is Mechanical Energy?

Mechanical energy can be described as the sum of the potential energy and kinetic energy in a system.

 

Only conservative forces are associated with mechanical energy. This includes forces like gravity and the spring force. Potential energy is associated with this kind of forces. Nonconservative forces like friction and drag do not fall in this category. With conservation forces, if they are added to a system, the energy imperatively retrieved. But on the other hand, recovering energy of the nonconservative forces is very difficult. This is because it often ends up as heat or some other form which mostly ends up outside the system. This can be also described as an energy being lost to the environment. 

 

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In terms of problems and calculations, this means that mechanical energy is much easier to be calculated and used to make predictions. But, it should be remembered that the conservation of mechanical energy only applies when all forces are conservative. Fortunately, in most cases, nonconservative forces can be ignored and included as part of the environment. A good approximation can be made even without adding up the non-conservative forces.

 

How can Conservation of Energy Explain the Movement of Objects?

When energy is conserved, it is possible to set up equations since we can equate the sum of the different forms of energy in a system. This allows us to solve the equations for velocity, distance, or any other parameter on which the energy depends. Another advantage of using the theorem of conservation of energy to solve problems is that even if we don’t know all the necessary variables to solve a certain type of problem, it might still be useful in understanding a situation, even in terms of variables. 

 

In a problem which discusses the case of a golfer on the moon striking a golf ball wherein the ball leaves the club at an angle of 45 degrees to the lunar surface traveling at 20 m/s both vertically and horizontally at a total velocity of 28.28 m/s. The question of how high the ball would go can be solved by using the equations associated with the law of conservation of energy and mechanical energy. Such equations are known as kinematic equations.

 

5 kinematic equations

1: S = Vt

2: [V_{f} = V_{i} + at]

3: [V_{av} = frac{V_{f} + V_{i}}{2}]

4: [S = V_{i}t + frac{1}{2} at^{2}]

5: [2as = V_{f}^{2} – V_{i}^{2}] 

 

Why can Perpetual Motion Machines Never Work?

The perpetual motion discusses the concept of a machine which continues its motion forever with a condition that there won’t be any reduction in speed. It is the dream of modern science. Though it seems really interesting such a machine cannot really work according to physics we have explored. In fact, even if such a machine were to exist, it wouldn’t be useful to anyone is what has been discovered .apparently, it would have no ability to do work. 

 

According to the principles of mechanics, a system, if it can be fully isolated from the environment and made to subject to only conservative forces, then energy would be conserved and it would run perpetually. The problem we would face is that that in reality, there is no way to completely isolate a system. Also, energy can never be completely conserved within the machine.

 

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Modern science has made extremely low friction flywheels. They rotate in a vacuum in order to store energy. Yet, we have seen that they still lose energy and eventually spin down when unloaded, over a period of years which can be predicted if other factors of the machine and environment are taken into consideration and calculated accordingly. Many physicists and researchers have thought of the earth itself as an extreme example of such a machine. While it rotates on its axis, interactions with the moon, tidal friction, and other celestial bodies, it too is gradually slowing. An unknown but very interesting and terrifying fact is, every couple of years, scientists add a leap second to our record of time to account for the variation in the length of day.

Light is a form of Electromagnetic Radiation of any Wavelength whether it is visible or not. Light is made up of small packets of energy called Photons, consisting of Waves of Electromagnetic Radiations. Photons do not possess any charge or resting mass and travel at the speed of Light. In Physics and optics, an idealized model of Light drawn as a straight line is called a Light Ray. A Light Ray is always drawn with an arrow that implies the direction of the energy flow. Light Rays are nothing but a model explaining the movements of Light from one point to another. A group of Light Rays or a Light Beam, coming out from a source of Light is known as a point source. 

 

Different Types of Beams of Light

Beams of Light can be of 3 types. They are parallel, convergent and divergent.

Parallel: When Rays from a distant point source travel parallel to each other in a particular direction, it forms a parallel Light Beam. The sunRay is an example of a parallel Beam of Light.

Convergent: In a convergent Beam, the Light Rays from a source of Light, eventually meet or converge to a point.

Divergent: In a divergent Beam, the Light Rays disperse away from a source of Light.

 

Reflection of Light

Light Rays change their direction while moving from one medium or when they are reflected off a surface. The law of Reflection states that a Light Ray reflecting off an even surface has an equal angle of incidence and angle of Reflection.

Refraction of Light

When a Light Ray travels from one transparent medium to another transparent medium, a portion of the Light is reflected and another portion of the Light is transmitted into the second transparent medium, changing the direction of the Light. This phenomenon is defined as the Refraction of Light. 

 

The law of Refraction or Snell’s law states that the ratio of the sine of angles of incidence and Refraction is equal to the ratio of the refractive index of the first and the second media respectively.

Mathematical Form

ratio of sin θ₁ and sin θ₂ (sin θ₁ / sin θ₂ ) = ratio of refractive index (n₁ / n₂)

 

or, 

 

n₁ sin θ₁ = n₂ sin θ₂

Where,

 

θ₁ = angle of incidence

 

θ₂ = angle of Refraction

 

The index of Refraction of medium 1 and 2 are n₁ and n₂, respectively

 

A Light Ray from a Lighter medium when entered into a denser medium bends towards the normal of the surface. On the other hand, a Ray emerging from a denser medium entering into a Lighter medium bends away from the normal. When the incident Ray is equal to the normal of the surface, the direction of the Light stays unaltered as it enters into the second medium.

Index of Refraction

The ratio of the speed of Light in a vacuum to its speed in that particular medium is known as the refractive index or index of Refraction. For example, the refractive index for a vacuum is always 1. The refractive index of air (standard conditions) is 1.0003, water is 1.3, and that of glass is 1.5.

 

By the law of Reflection and the law of Refraction, you can understand how a Light Ray travels. The law of Reflection can be used to understand the images produced by different types of mirrors like a plane mirror, concave and convex mirrors. Whereas, Snell’s law can be used in lenses. For example, a human eye.

 

Light can be described as an Electromagnetic Wave where the straight-line paths that are followed by narrow Beams of Light through which Light energy travels are commonly known as Rays. Light travels in straight lines but its direction can be changed by Reflection or Refraction. Light is made up of energy called photons,  which consists of Waves of Electromagnetic Radiation. A model which explains the movement of Light from one place to another is what Light Ray is.

Different Types of Light Rays

There are three different types of Light Beams, namely Parallel. Convergent and Divergent A Beam of Light Rays that are given out from a source is known as a Beam of Light.

While moving from one medium, or when Light is reflected off a surface, Light Rays change their direction. On Reflection from a smooth surface, the angle of the Ray that is reflected is equal to the incident Ray’s angle.  This law of Reflection is used to understand the complex images that are produced by the plane and the curved mirrors.

A Ray of Light travels from one transparent medium to another, and one portion of the Light is reflected, and another portion of the Light is transmitted to another second transparent medium – this phenomenon is known as Refraction.

The law of Refraction is also known as Snell’s law.

With the help of certain mathematical formulas, the various problems on Light, a Ray of Light and a Beam of Light, can all be solved.