Coherent sources are those sources for which

Write the condition of destructive interference in terms of path and phase difference.

The ratio of the amplitudes of two interfering waves is $3 : 4$. What is the ratio of their intensities?

Two light waves of intensities $I$ and $2I$ superimpose on each other. If the path difference between the light waves reaching a point is $12.5 \%$ of the wavelength of the light,then the resultant intensity at the point is (Both the light waves have same wavelength).

If the ratio of amplitudes of two interfering waves is $4: 3$,then the ratio of maximum and minimum intensity is

$A$ and $B$ are two interfering sources where $A$ is ahead in phase by $54^{\circ}$ relative to $B$. The observation is taken from point $P$ such that $PB-PA=2.5 \lambda$. Then the phase difference between the waves from $A$ and $B$ reaching point $P$ is (in rad) (in $\pi$)