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The interference pattern is obtained with two coherent light sources of intensity ratio n. In the interference pattern, the ratio (Iₘₐₓ-Iₘᵢₙ)/(Iₘₐₓ+Iₘᵢₙ) will be

Asked in NEET 2016 · Intensity and coherent sources

Answer: (2) (2√n)/(n+1)

Step-by-step solution

Given: the two sources have intensities in the ratio (I₂)/(I₁)=n.

Idea: write Iₘₐₓ and Iₘᵢₙ in terms of the amplitudes √I₁ and √I₂, which add and subtract.

Iₘₐₓ=(√I₁+√I₂)² and Iₘᵢₙ=(√I₁-√I₂)².

Numerator: the difference of those two squares is 4√I₁I₂.

Denominator: their sum is 2(I₁+I₂).

Ratio =(4√I₁I₂)/(2(I₁+I₂))=(2√n)/(n+1) after dividing through by I₁.

Why the other options are wrong

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