Monochromatic light is refracted by a glass prism. Which of the following quantities is always the same for the light both inside and outside of the prism?

#1

Amplitude.

#2

Speed.

#3

Frequency.

#4

Wavelength.

Amplitude

Explanation:

The main change occurs in the speed of light when changed from inside to outside prism. Since we knkw that speed is a product of wavelength and velocity, then ultimately these two factors also change.

Speed=wavelength*frequency

From the above, it is only amplitude which will not be affected since it has no relationship with speed, frequency and wavelength. The period of the wave, T will also be affected since period is reciprocal of frequency.