Question

Two coherent monochromatic light beams of intensities $I$ and $9I$ are super imposed. The maximum and the minimum intensities of the resultant beam are:

• A. $10I$ and zero
• B. $10I$ and $8I$
• C. $10I$ and $4I$
• D. $16I$ and $4I$
• E. $16I$ and zero

Answer 1

Answer: (D)

The ratio of maximum to minimum intensity is $\frac{I_{\max }}{I_{\min }}=\frac{{(\sqrt{I_1}+\sqrt{I_2})}^2}{{(\sqrt{I_1}-\sqrt{I_2})}^2}=\frac{{(1+3)}^2}{(1-3)}=\frac{4^2}{2^2}$ $=\frac{16}{4}$