Question

What are the conditions for destructive interference to occur?

Answer 1

Interference

1. It is a phenomenon in which two waves superpose with each other to form a resultant wave that has lower, higher or the same amplitude.
2. There are two types of wave interference, constructive interference, and destructive interference.

Destructive interference:

1. Destructive interference is the case in which two waves superimpose giving rise to a wave of very less or negligible intensity.

Condition for destructive interference

1. It occurs when the maxima of two waves are $180°$ out of phase, i.e., a positive displacement in one wave is canceled out by negative displacement in the other wave.
2. Or path difference should be, $\delta =\left(n+\frac{1}{2}\right)\lambda$ where $\lambda$ is the wavelength.
3. In the figure, we can see that the two waves are in $180°$ phase difference. Here, the amplitude of the resultant wave(here shown in red) is equal to zero.