Question

18 State two differences between the effect of a prism and a parallel glass slab on the
incident white light Which colours of light undergo maximum and minimum deviation?
What will be your observation if you look at the sky through a water fountain with the
Sun behind your head?​

Answer 1

Answer:

if u look at the fountain behind Sun u will see a rainbow

Answer 2

White light is dispersed by a prism and not by the glass slab.The red colour is the least deviated and violet colour is most deviated.Formation of rainbow occurs when one looks sky through fountain with sun behind his head

Explanation:

1. The two main differences between the effect of a prism and a parallel glass slab on the incident white light are:-

• When white light is incident on a prism,dispersion of light takes place.Dispersion of light refers to the splitting up of light into the seven components it is made up of.Whereas,when white light is incident on a glass slab it refracts the light through it with a little displacement.

• In prism the incident ray is not parallel to the emergent ray as it makes some angle between them known as angle of deviation.Whereas,in glass slab the incident ray is parallel to the emergent ray with a slight displacement.

  2.The wavelength is of a light is inversely proportional to the deviation it suffers.Hence ,the red colour has the greatest wavelength and so undergoes least deviation.Whereas,the colour violet has lowest wavelength and so undergoes maximum deviation.

 3. When light moves from air to water ,the speed slows down and the light appears to bend known as refraction.Since, the white light is made up of seven colours and each colour bend at different angles. Hence, there will be formation  of a rainbow when one look at the sky through a water fountain with the sun behind head.