Two separated sources emit sinusoidal travelling waves but have the same wavelength `lambda` and are in phase at their respective sources . One travels a distance `l_(1)` to get to the observeration point while the other travels a distance `l_(2)` . The amplitude is minimum at the observation point , `l_(1) - l_(2)` is an

Options

A. odd integral multiple of `lambda`
B. even integral multiple of `lambda`
C. odd integral multiple of `lambda//2`
D. odd integral multiple of `lambda//4`

Answer

C

Explanation

For destructive interference , path difference has to be equal to an odd integral multiple of `lambda//2`.