Question

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

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

Answer 1

Answer: (C)

9 I and I

Answer 2

I_max. = I₁ + I₂ + 2$\sqrt{I_{1}I_{2}}$

= I + 4 I + 2$\sqrt{I \times 4I}$ = 9 I

I_min. = I₁ + I₂ – 2$\sqrt{I_{1}I_{2}}$

= I + 4 I – 2$\sqrt{I \times 4I}$ = I