Question

A red colour in air has wavelength 760 nm when light passes through water of refractive index $(n=\frac{4}{3})$, wavelength becomes 570 nm.(wavelength of yellow colour in air is 570 nm).Then colour of red light in water is

• A. Red
• B. Green
• C. Yellow
• D. Blue

Answer 1

Answer: (A)

Red

Frequency determines the color of light. The frequency of light does not change upon refraction. To keep the frequency unchanged on refraction, the wavelength must decrease by division by the refractive index. So the color of light do not change.