JEE Advanced 2008 Physics question

In a Young's double slit experiment, the separation between the two slits is d and the wavelength of the light is λ. The intensity of light falling on slit 1 is four times the intensity of light falling on slit 2. Choose the correct choice(s).

(A)If d = λ, the screen will contain only one maximumCorrect
(B)If λ < d < 2λ, at least one more maximum (besides the central maximum) will be observed on the screenCorrect
(C)If the intensity of light falling on slit 1 is reduced so that it becomes equal to that of slit 2, the intensities of the observed dark and bright fringes will increase
(D)If the intensity of light falling on slit 2 is increased so that it becomes equal to that of slit 1, the intensities of the observed dark and bright fringes will increase

Answer: (A),(B)

Solution

Maxima occur at with . (A) d = λ: only n = 0 is possible (n = ±1 would need θ = 90°): one maximum. (B) λ < d < 2λ: n = ±1 gives , so first-order maxima appear. (C) With , bright = \sqrt{4I_2}\sqrt{I_2}$

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Question ID VK-037568