Question

Why is the amount of the momentum transferred by the em waves incident on the surface so small ?

Answer 1

Momentum transferred = \[\frac{\text { Energy}}{\text { Speed of light }} = \frac{h\nu}{c}\] \[\approx\] (for \[\nu~ {10}^{20}\]  Hz)
Thus, the amount of the momentum transferred by the em waves incident on the surface is very small.