Question

A medium is said to be dispersive if ____

• A. Light of different wavelengths propagate at different speeds
• B. Light of different wavelengths propagate at same speed but has different frequencies
• C. Light is gradually bent rather than sharply refracted at an interface between the medium and air
• D. Light is never totally internally reflected

Answer 1

The correct option is A Light of different wavelengths propagate at different speeds

The splitting of white light into its component colours when passing through a refractive medium is Dispersion'. The cause of this phenomenon is the change in the speed of light with wavelength. ie., in a refracting medium, lights of different colour travel at different speed. The speed of violet colour(least wavelength) is the least and of the red colour(greatest wavelength) is the greatest. For example, when light travels from air into water, it slows down, causing it to continue to travel at a different angle or direction and so they split into the colour spectrum.