Question

Does amplitude of light change during refraction if reflection also happens

Answer 1

If you use Maxwell's equations and assume the incoming waves are plane waves and polarized in one direction you can show that some of the amplitude of the initial electromagnetic radiation (light) is refracted and some is reflected.

Answer 2

Explanation:

So the incident amplitude is equal to the reflected amplitude and the refracted amplitude is zero. ... When light waves are reflected in denser medium, they suffer a phase change of 180° but if they are reflected in rarer medium, no change in phase is seen.