Question

Light waves travelling through air strike the surface of water at an angle. Which of the following statements about the lights wave properties upon entering the water is correct?

• A. The light's speed, frequency and wavelength all stay the same
• B. The light's speed, frequency and wavelength all change
• C. The light's speed speed and frequency change, but the wavelength stays the same
• D. The light's wavelength and speed changes, but the frequency stays the same

Answer 1

Answer: (D)

The light's wavelength and speed changes, but the frequency stays the same

Frequency of light remains the same in all mediums.

Since water is optically denser medium, speed of light reduces in water.

But, speed is given by $v=f\lambda$ i.e. $v\propto \lambda$

Hence, wavelength also reduces in water.