Question

Two coherent light beams of intensity I and 4I are superposed. The maximum and minimum possible intensities in the resulting beam are.

• A. $9$I and I
• B. $9$I and $3$I
• C. $5$I and I
• D. $5$I and $3$I

Answer 1

The correct option is A $9$I and I

Given,

$\frac{I_1}{I_2}={\left(\frac{a_1}{a_2}\right)}^2=\frac{1}{4}\frac{a_1}{a_2}=\frac{1}{2}\Rightarrow a_2=2a_1--------\left(i\right)\frac{I_{max}}{I_{min}}=\frac{(a_1+a_2{)}^2}{(a_1-a_2{)}^2}=\frac{(a_1+2a_1{)}^2}{(a_1-2a_1{)}^2}={\left(\frac{3a_1}{-a_1}\right)}^2=\frac{9}{1}$

Hence the required possible intensities will be 9I and I.