Q125 / 180 · NEET 2016 (Phase 2) · Physics

The interference pattern is obtained with two coherent light sources of intensity ratio, $n$ . In the interference pattern, the ratio, $\frac{I_{\max} - I_{\min}}{I_{\max} + I_{\min}}$ will be

Solution

$\frac{I_{1}}{I_{2}} = n$ .

$I_{\max} = {(\sqrt{I_{1}} + \sqrt{I_{2}})}^{2} = {(\sqrt{n} + 1)}^{2} I_{2}$ .

$I_{\min} = {(\sqrt{I_{1}} - \sqrt{I_{2}})}^{2} = {(\sqrt{n} - 1)}^{2} I_{2}$ .

$\frac{I_{\max} - I_{\min}}{I_{\max} + I_{\min}} = \frac{4 \sqrt{n}}{2 (n + 1)} = \frac{2 \sqrt{n}}{n + 1}$

Hence, the correct answer is option: 'B'.