Question

state a condition for no refraction of light when light enters frm 1 medium 2 another

b)what is the cause of dispersion of light passing through a prism?

Answer 1

When light enters from one medium to another at angle of incidence (i) greater than the critical angle (C), then total internal reflection will occur and no refraction takes place (but also for total internal reflection to take place, the second medium should be denser)

b) White light is made up of seven constituent colours which are vibgyor. Each of these individual light beams have different wavelengths and they differ in the rate of deviation when they pass from one transparent medium to another transparent medium and they also differ on the matter of the speed with which they travel when they change their medium. So when the white light passes through the prism, on the first surface of prism these light beams get distinguished because they differ in their rate of deviation and therefore we see the spectrum of seven colours, and when these individual beams strike the second surface of the prism refraction occurs for each of the beams. So to summarise, on the first surface of the prism dispersion of light occurs and on the second surface refraction occurs and this is the whole phenomenon.