A short pulse of white light is incident from air to a glass slab at normal incidence. After travelling through the slab, the first colour to emerge is.

Options

A. blue
B. green
C. violet
D. red

Answer

4

Explanation

As velocity of wave is given by the relation v = f`lambda`. When light ray goes from one medium to other medium, the frequency of light remains unchanged. Hence v `prop lambda` or greater the wavelength, greater the speed.
The light of red colour is ofhighest wavelength and therefore, after travelling through the slab, the red colour emerges first.