Question

Two coherent monochromatic light beams of intensities '$4I$' and '$9I$' are superimposed. The maximum and minimum possible intensities in the resulting beam are

• A. $3I$ and $2I$
• B. $9I$ and $5I$
• C. $16I$ and $3I$
• D. $25I$ and $I$

Answer 1

Answer: (D)

$25I$ and $I$

Maximum intensity $I_{max}=(\sqrt{I_1}+\sqrt{I_2}{)}^2$

Or $I_{max}=(\sqrt{4I}+\sqrt{9I}{)}^2$

Or $I_{max}=(2+3{)}^{2}I=25I$

Minimum intensity $I_{min}=(\sqrt{I_1}-\sqrt{I_2}{)}^2$

Or $I_{max}=(\sqrt{4I}-\sqrt{9I}{)}^2$

Or $I_{max}=(2-3{)}^{2}I=I$