Question

You are given four sources of light each one providing a light of a single colour-red, blue,green and yellow. Suppose the angle of refraction for a beam of yellow light corresponding to a particular angle of incidence at the interface of two media is `90^@`. Which of the folowing statements is correct it the source of yellow light is replaced with that of other lights without changing the angle of incidence ?
A. The beam of red light would undergo total internal reflection.
B. The beam of red light would bend towards normal while it gets refracted through the second medium.
C. The beam of blue light would undergo total internal reflection.
D. The beam of green light would bend away from the normal as it gets refracted through the second medium.

Answer 1

Correct Answer - C
Here, for yellow light, `r = 90^@` when `i = C` As `i` is kept same. `C` must be smaller for total internal reflection. From `mu = (1)/(sin C), C` will be smaller, when br smaller, when `mu` is larger. Out of given colours, `mu` is largest for blue colour. Critical angle will be smallest for blue colour. Therefore, blue light would undergo total internal reflection. Choice ( c) is correct.