What are the important effects which arises due to superposition of waves ?

Answer

The superposition of two waves gives rise to the following important effects :
1. When two waves of same frequency (or wavelength) moving with the same speed and in the same direction superpose on each other, they give rise to to an effect, called interface of waves.
2. When two waves of the same frequency moving with the same speed in oppsite direction superpose on each other, they give rise to stationary waves.
3. When two waves of slightly different frequency moving with the same speed in the same direction superpose on each other, they give rise to beats.