Question

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

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

Answer 1

Answer: (C)

9I and I

Answer 2

$I_{max}=(\sqrt{I_1}+\sqrt{I_2})^2=(\sqrt{4I}+\sqrt I)^2=9I$ $I_{min}=(\sqrt{I_1}-\sqrt{I_2})^2=(\sqrt{4I}-\sqrt I)^2=I$ $\therefore$ Correct option is (c ).