Question

A ray of white light is incident on the interface of glass and air, as shown. The angle of incidence is such that green light just suffers total internal reflection. The ray of light emerging from glass to air contains:

Options

• yellow, orange and red

• violet, indigo and blue

• all colours

• all colours except green

Answer 1

Yellow, orange and red

Explanation:

Green light just suffers total internal reflection, so it doesn’t emerge. Wavelengths longer than green (yellow, orange and red) have a larger critical angle and thus pass through (emerge) without total internal reflection. Shorter wavelengths (violet, indigo and blue) are totally internally reflected, along with green. Hence, the emerging ray contains yellow, orange and red light only.