Question

At a point having a path difference of $\frac{\lambda }{4}$, the intensity will be

• A. $0$
• B. $a^2$
• C. $2a^2$
• D. $a^2/2$

Answer 1

The correct option is B $a^2$

Using $\varphi =\frac{2\pi }{\lambda }\Delta x$

Path difference, $\Delta x=\frac{\lambda }{4}$ gives $\varphi =\frac{\pi }{2}$

Now as $I=2a^{2}co{s}^2\left(\frac{\varphi }{2}\right)$

This gives $I=a^2$