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

The correct option is B red
As we know,

Velocity of wave is given by

$v=f\lambda$…(𝑖)

When light ray goes from one medium to other medium, the frequency of light remains unchanged.

From equation(𝑖)

$v\alpha \lambda$

i.e.,velocity of wave is directly proportional to the wavelength of light means greater the wavelength, greater the speed.

The light of red colour has the highest wavelength and therefore has highest speed. Therefore, after travelling through the slab, the red colour emerges first.

Final Answer: (𝑑)