° In a double-slit experiment, green light (5303 Å) falls on a double slit having a separation of 19.44 μ m and a width of 4.05 μ m. The number of bright fringes between the first and the second diffraction minima is: (a) 04 (b) 05 (c) 10 (d) 09

Answer: (b). Diffraction minima: sin θ = (λ)/(a), (2λ)/(a); bright fringes: sin θ = (mλ)/(d) Between the minima: d/a < m < 2d/a, with d/a = (19.44)/(4.05) = 4.8 4.8 < m < 9.6 ⇒ m = 5, 6, 7, 8, 9 So the answer is (b) 5 bright fringes.

° In a double-slit experiment, green light (5303 Å) falls on a double… | JEE Main 2019 (11 Jan, Shift 2)

Q71JEE Main 2019 · 11 JAN · SHIFT 2Difficult

Diffraction at a Single Slit

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In a double-slit experiment, green light (5303 $\text{Å}$ ) falls on a double slit having a separation of 19.44 $\mu$ m and a width of 4.05 $\mu$ m. The number of bright fringes between the first and the second diffraction minima is:

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Answer: (b)

Diffraction minima: $\sin\theta = \dfrac{\lambda}{a}, \dfrac{2\lambda}{a}$ ; bright fringes: $\sin\theta = \dfrac{m\lambda}{d}$
Between the minima: $\dfrac{d}{a} < m < \dfrac{2d}{a}$ , with $\dfrac{d}{a} = \dfrac{19.44}{4.05} = 4.8$
$4.8 < m < 9.6 \Rightarrow m = 5, 6, 7, 8, 9$
So the answer is (b) 5 bright fringes.

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Diffraction at a Single Slit question from JEE Main 2019 (11 Jan, Shift 2)

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