Question

Two identical light waves, propagating in the same direction, have a phase difference $\delta$. After they superpose the intensity of the resulting wave will be proportional to

• A. $\cos \delta$
• B. $\cos \left(\frac{\delta }{2}\right)$
• C. ${\cos }^2\left(\frac{\delta }{2}\right)$
• D. ${\cos }^2\delta$

Answer 1

The correct option is C ${\cos }^2\left(\frac{\delta }{2}\right)$

Maximum intensity,
$I=4I_0{\cos }^2\left(\frac{\delta }{2}\right)$
$\Rightarrow I\propto {\cos }^2\left(\frac{\delta }{2}\right)$