Question

In the case of light waves from two coherent $S_1$ and $S_2$ there will be constructive interference at an arbitrary point $P$, if the path difference $S_{1}P-S_{2}P$ is

• A. $\left(n+\frac{1}{2}\right)\lambda$
• B. $n\lambda$
• C. $\left(n-\frac{1}{2}\right)\lambda$
• D. $\frac{\lambda }{2}$

Answer 1

Answer: (B)

The path difference $S_{1}P-S_{2}P$
is a whole number of wavelength, the fringe at $P$ is dark no bright.
So, $S_{1}P-S_{2}P=n\lambda$ (for minimum intensity)