Question

what is cause of dispersion

Answer 1

The dispersion of a light pulse as it travels through a media is due to the refractive index being different for different wavelengths, and a pulse is composed of many different wavelengths.

Answer 2

Answer:

Light rays of different colours,travel with the same speed in vacuum and air but in any other medium,they travel with different speeds and bend through different angles, which leds to dispersion of light.

Red light has maximum wavelength and violet light has the minimum wavelength. So in medium, red light travels fastest and deviates least, while violet light travels slowest and deviates maximum