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Refrection of light and laws of refrection.

Refrection of Light - Laws of Refrection - Couse & Effects - JK STUDY NOTES

What is Refrection of Light. What is Couse of Reftection. What are the Effects of Refrection of Light. What are the Laws of Refrection. First Law of
What is Refrection of Light. What is Couse of Reftection. What are the Effects of Refrection of Light. What are the Laws of Refrection. First Law of Refrection. Second Law of Refrection.

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Refrection of light


What is Refrection of Light

We know that Light travelled in a stright line this is tree on when light travels in only same medium and having a same density. When a light rays travells in one madium to another madium, the light rays changes their direction or bend at the boundary between the two medium. For example when a light travells in air and if it now travells into another medium i.e glass it changes its direction when it enter the glass. So the Refrection of Light is defined as the changing of direction of light rays when it goes to one medium to another medium. The refrection of light can also be defined as bending of light when it passes to one medium to another medium.

The reflection of light is takes place when the light enters from air to water or from water to glass. The instruments like Camera, Microscope and Telescope all works on the principle of refrection of light through glass lens.

Please note that in reflection of light, the angle of reflection is always equal to the angle of incidence but in refrection of light, the angle if refrectionis usually not equal to the angle of incidence. It will be either smaller then angle of incidence or greater than angle of incidence.

What is Couse of Refrection

The speed of light is not same in every medium. It is different in different medium. If we see the speed of light in air i.e 3×10⁸ m/s where as the speed of light in glass i.e 2×10⁸ m/s. It will clear the the speed of light is not same in different medium. The speed of light in air is more then the speed of light in glass. It proofs that the speed of light is faster in air then glass. Now we can say that the refrection of Light is also takes place due to the of speed of light when runs one medium to another medium. Please note that greater the difference of speed of light in two medium greater will be the amount of refrectionof light.

Please note that when the ray of light travels from glass medium to air medium it bends from the normal and if we see the other hand when ever the ray of light travelling in air and enters into air, it bends away from the normal this is becouse water is optically denses than air.

What are the Effects of Refrection of Light

There are many effects of refrection of light which we easily observe in our daily life. These effects of refrection are :

A stick or pencil  appears to bend at the water surface when it is held obliquely or partly immersed in water.

An any objects that is placed under the water appears raised.

Due to refrection of light a pool of water appears to be less deep then the actually it is.

When a think glass slab is placed over some printed matter, the latters appears bigger when viewed from the top.

Due to refrection of light the stars appears to twinkle on a clean night.

When a lemon is keep in water in a glass tumbler appears to be bigger then actually it is when viewed from the sides.

What are the Laws of Refrection

The refrection of light is done on going from one medium to another medium takes place according to two laws which are known as the laws of refrection of light. These laws are:

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Laws of Refrection of light


First Law of Refrection 

According to first law of refrection the incident ray, the refracted ray and the normal at the point of incidence all lie in the same plane.

Second Law of Refrection

According to second law of refrection the relationship between the angle of incidence and the angle refrection. This relationship was discovered by Snell Experimentally in 1621, so the second law of refrection is called Snells law of refrection. According to snall's law of refrection of light The ratio of sine of angle of incidence to the sine of angle of refrection is constant for a given pair of medium. That is 

     Sine of angle of incidence
          ———————————                 =  Constant
     Sine of angle of refrection

                              Sine i
                       ——–   =  Constant
                        Sine r

This "constant" is called refrective index.

The value of the contant sin i /sine r for a ray of light passing from air into a particular medium is called Refrective Index of that medium.