Physics - Wave on String Question with Solution | TestHub

The net intensity due to interference of two beams of intensities ${\mathrm{I}}_1,{\mathrm{I}}_2$ with a phase difference of $\varphi$ is ${\mathrm{I}}_{\text{net }}={\mathrm{I}}_1+{\mathrm{I}}_2+2\sqrt{{\mathrm{I}}_1}\sqrt{{\mathrm{I}}_2}\cos \varphi$ Thus, ${\mathrm{I}}_{{\text{net }}_{\text{max }}}$ occurs for $\cos \varphi =1$ $\Rightarrow {\mathrm{I}}_{{\text{net }}_{\max }}={\left(\sqrt{{\mathrm{I}}_1}+\sqrt{{\mathrm{I}}_2}\right)}^2=9\mathrm{I}$ Similarly, ${\mathrm{I}}_{{\text{net }}_{\min }}$ occurs for $\cos \varphi =-1$ $\Rightarrow {\mathrm{I}}_{{\text{net }}_{\min }}={\left(\sqrt{{\mathrm{I}}_1}-\sqrt{{\mathrm{I}}_2}\right)}^2=\mathrm{I}$