Answer the following questions in short :


1. State the laws of refraction.
Ans. 1.
The incident ray and the refracted ray are on the opposite sides of the
normal at the point of incidence and all three lie in the same plane. 2. For a given pair of media, the ratio of the sine of the angle of incidence
to the sine of the angle of refraction is constant.
If ‘i’ is the angle of incidence and ‘r’ is angle of refraction then,

sini
sinr = Constant.

2. How are rainbows formed ?
Ans.
1. The rainbow appears in the sky after a rain shower.

2. The water droplets act as small prism.
3. When sunlight enters the water droplets present in the atmosphere,

they refract and disperse the incident sunlight. Then they reflect it
internally inside the droplet and finally again refract it.
4. As a collective effect of all these phenomena the seven coloured rainbow

is formed.
*3. What do you mean by dispersion ? Name the different colours of light in the proper sequence in the spectrum of light.
Ans. 1. The phenomenon of splitting of light into its component colours is called as dispersion.
2. The band of coloured components of light beam is called as spectrum. The colours in the order from bottom to top are violet, indigo, blue, green, yellow, orange, red (VIBGYOR).
*4. What is refraction of light ? How it is related to refractive index ? Ans. 1. The phenomenon of change in the direction of light when it passes
from one transparent medium to another is called refraction.
2. The extent of change in the direction of the light ray is different for

different media and is related to the refractive index of the medium.