Question

Two coherent monochromatic light beams of intensities I and 4I are superposed. The maximum and minimum possible intensities in the resulting beam are
[IIT-JEE 1988; RPMT 1995; AIIMS 1997; MP PMT 1997;MP PET 1999; BHU 2002; KCET 2000, 05]

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

Answer 1

The correct option is C

9I and I

$I_{max}={(\sqrt{I_1}+\sqrt{I_2})}^2={(\sqrt{I}+\sqrt{4I})}^2=9I$
$I_{min}={(\sqrt{I_1}-\sqrt{I_2})}^2={(\sqrt{I}-\sqrt{4I})}^2=I$