question_answer

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)  \[\frac{\lambda }{2}\]

Correct Answer: B

Solution :

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)