Q. Two waves of equal amplitude and frequency interfere each other. The ratio of intensity when the two waves arrive in phase to that when they arrive $90{^\circ}$ out of phase is
A) 1 : 1
B) $\sqrt{2}\ :1$
C) 2 : 1
D) 4 : 1
Explanation
(c) Resultant intensity $I = 4I_{0}\cos^{2}{(\phi/2)}$
$\Rightarrow \frac{I_{1}}{I_{2}} = \frac{\cos^{2}{(\phi_{1}/2)}}{\cos^{2}{(\phi_{2}/2)}} = \frac{\cos^{2}0}{\cos^{2}{(90/2)}} = \frac{2}{1}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.