Two monochromatic light beams have intensities in the ratio 1:9. Their interference pattern is observed. The ratio of maximum to minimum intensity is:
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Question

Two monochromatic light beams have intensities in the ratio 1:9. Their interference pattern is observed. The ratio of maximum to minimum intensity is:

G1 Physics · Accepted Answer

Intensity is proportional to the square of amplitude. Given, I₁:I₂ = 1:9. Therefore, A₁:A₂ = 1:3. Maximum intensity: I m a x I_max I m ​ a x ∝ (A₁+A₂)² = (1+3)² = 16. Minimum intensity: I m i n I_min I m ​ in ∝ (A₂-A₁)² = (3-1)² = 4. Hence, I m a x : I m i n I_max:I_min I m ​ a x : I m ​ in = 16:4 = 4:1. Correct option: D.