Question

Two light beams produce interference pattern to give maxima and minima on the screen. If the intensities of the light beams are in the ratio of 9: 4, then the ratio of intensities of maxima and minima is

• A. 3 : 2
• B. 5 : 1
• C. 25 : 1
• D. 9 : 1

Answer 1

Answer: (C)

$ \frac{{{I}_{1}}}{{{I}_{2}}}=\frac{a_{1}^{2}}{a_{2}^{2}} $ $ \therefore $ $ \sqrt{\frac{9}{4}}=\frac{{{a}_{1}}}{{{a}_{2}}} $ $ \Rightarrow $ $ \frac{{{a}_{1}}}{{{a}_{2}}}=\frac{3}{2} $ $ \therefore $ $ \frac{{{I}_{\max }}}{{{I}_{\min }}}=\frac{{{({{a}_{1}}+{{a}_{2}})}^{2}}}{{{({{a}_{1}}-{{a}_{2}})}^{2}}}={{\left( \frac{3+2}{3-2} \right)}^{2}} $ or $ {{I}_{\max }}:{{I}_{\min }}=25:1 $