6th Class Science Light, Shadows and Reflections Refraction of Light

       Refraction of Light

Refraction of light occurs, when it posses from one medium to another. Let's study about it in detail.

             Refraction of Light in Transparent Glass

We are able to see things because of the light. Light can travel through any transparent medium. When a beam of white light enters into a transparent glass from air, the path of the white light gets tilted at an angle. This feature of light is called the refraction of light.

Look at the following picture of refraction of light in a glass medium:

In the picture above \[{{\theta }_{1}}\] is the angle of incident with respect to the normal and \[{{\theta }_{2}}\] is the angle of refraction.

Refraction of light or angle of refraction in a medium depends on the refractive index or speed of light in that medium. The refractive index of a substance is the ratio of velocity of light in vacuum to the velocity of light in that medium.

A transparent glass passes the incident beam of light through it. But a glass with one side painted cannot allow the light to pass through it.

           Refraction of Light in Water

When light enters into the water from air, the incident ray is refracted by the water at an angle. Angle of refraction with respect to the normal is increased due the impurities in the water.

In the picture above a stick in the water is observed by an observer. The stick appears upward from its position because of the refraction of light.

           Dispersion of Light

Look at the following picture of dispersion of light by a prism:

In the picture above, AB is the incident beam of white light. AB is dispersed into seven colours when passed through a prism. The detector (white screen) detects the dispersed light into seven visible colours and the order of least deviation to maximum deviation of colours of light is same as the given in the picture above. The rays, which have smaller wave length than violet, are called ultra violet rays and the rays which have greater wavelength than red are called infra red rays. Both the rays, ultraviolet and infrared are invisible to the naked eyes. The band of these seven colours which is obtained in the dispersion phenomena is called spectrum.

The formation of rainbow in the sky is based on the dispersion of light.

           Rainbow formation

Rainbow formation is a natural phenomenon. When Sun rays strike on the small water droplets in the atmosphere, it splits into many colours. But the visible colours is only from violet to red (VIBGYOR). Therefore, rainbow in the sky looks like a band of seven colours.

      What is called the bending of a beam of light when it passes from one medium to another medium?

(a) Refraction of light

(b) Law of reflection

(c) Reflection of light

(d) All of these

Answer: (a)

Explanation

The bending of a beam of light when it passes from one medium to another medium is known as the refraction of light. Therefore, option

(a) is correct and rest of the options is incorrect.  

     What will happen when two parallel beams of light pass from one medium to another medium?

(a) Both angle of refraction will be equal

(b) Both angle of refraction will be unequal

(c) Parallel beams of light cannot be refracted

(d) All of these

(e) None of these

Answer: (a)

Explanation

When two parallel beams of light pass from one medium to another, the angle of refraction for both the beams of light are equal. Therefore option (A) is correct and rest of the options is incorrect..