Answer : (A) amplitude
Explanation :
When two waves interfere in the same medium, then the amplitude of the resultant wave changes.
There are two conditions for interference :
(1) Constructive interference occurs when two waves are moving in the same direction. As a result, the amplitude gets larger.
(2) Destructive interference occurs when two waves are moving in opposite direction. As a result, both waves cancel out each other.
Hence, the correct option is (A).
