Physics - Wave on String Question with Solution | TestHub

The resultant intensity $I_R$ in interference is given by the formula:

$I_R=I_1+I_2+2\sqrt{I_1{I}_2}\cos \varphi$

Given $I_1=I$, $I_2=4I$, and $\varphi =\pi$.

Substituting these values into the formula:

$I_R=I+4I+2\sqrt{I\times 4I}\cos \pi$

Since $\cos \pi =-1$:

$I_R=5I+2\sqrt{4I^2}(-1)$

$I_R=5I-2(2I)$

$I_R=5I-4I=I$

Answer: I