Light rays bend as they pass from air into
water at an angle (not 90 degrees). This is
refraction.
Which quantity doesn’t change when light
refracts?
1. average speed of light
2. wavelength of light
3. index of refraction of the material
4. frequency of light

4

Explanation:

Refraction is the bending of light when it moves from one medium to another.

In the situation described:

The average speed of light changes when it goes to another medium. The speed of light in water is less than in air.When velocity/speed changes, the index of refraction changes as well. Water's index is greater than in air.Since, speed changes, wavelength changes too.Only the frequency remains the same. The rates of vibration stays the same.

Correct choice is #4.