Q.Two sound waves of equal amplitude $3\ \text{cm}$ and the same frequency arrive at a point with a constant phase difference of $60^\circ$. Find the amplitude of the resultant wave at that point.

Principle of Superposition of Waves

The principle of superposition states that when two or more waves overlap in a medium, the resultant displacement at any point and instant is the vector sum of the displacements that each wave would produce independently:

The waves pass through one another without being permanently altered; after crossing, each continues as if the others were absent, and no energy is lost in the overlap. Superposition applies to all kinds of waves — mechanical, sound and electromagnetic — not just to a special class. …