The phenomenon of interference is exhibited by:

In the adjacent diagram,$CP$ represents a wavefront and $AO$ & $BP$ are the corresponding two rays. Find the condition on $\theta$ for constructive interference at $P$ between the ray $BP$ and the reflected ray $OP$.

If two sources emit light waves of different amplitudes, then in the interference pattern:

Two monochromatic light beams have intensities in the ratio $1 : 9$. An interference pattern is obtained by these beams. The ratio of the intensities of maximum to minimum is (in $: 1$)

In the figure,the intensity of waves arriving at $D$ from two coherent sources $S_1$ and $S_2$ is $2I_0$ each. The wavelength of the wave is $\lambda = 8\,m$. The resultant intensity at $D$ will be:

In the phenomenon of interference: