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)