Question

What are the conditions for maxima and minima in case of Young's double slit experiment?

Answer 1

The two waves interfering at P have covered different distances $AP=x$ and $BP=x+\Delta x$.
For maxima,
$\Delta x=n\lambda$
For minima,
$\Delta x=(n+\frac{1}{2})\lambda$
where $n$ is an integer.