A beam of light having wavelength 5400 from a distant source falls on a single slit 0.96 mm wide and the resultant diffraction pattern is observed on a screen 2 m away. What is the distance between the first dark fringe on either side of central bright fringe? (a) 4.8 mm (b) 1.2 mm (c) 2.4 mm (d) 3.6 mm

Answer: (c). Distance between first dark fringes on either side: W = (2Dλ)/(a). W = 2 × 2 × 5400×10⁻¹⁰0.96×10⁻³ = 2.25×10⁻³ m 2.25 mm is closest to the given option 2.4 mm. So the answer is (c) 2.4 mm.

A beam of light having wavelength 5400 from a distant source falls on… | MHT CET 2021 (24 Sep, Shift 1)

Q56MHT CET 2021 · 24 SEP · SHIFT 1Easy

Diffraction at a Single Slit

A beam of light having wavelength $5400\text{ \AA}$ from a distant source falls on a single slit $0.96\text{ mm}$ wide and the resultant diffraction pattern is observed on a screen $2\text{ m}$ away. What is the distance between the first dark fringe on either side of central bright fringe?

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Answer: (c)

Distance between first dark fringes on either side: $W = \dfrac{2D\lambda}{a}$ .
$W = \dfrac{2 \times 2 \times 5400\times10^{-10}}{0.96\times10^{-3}} = 2.25\times10^{-3}\text{ m}$
$2.25\text{ mm}$ is closest to the given option $2.4\text{ mm}$ .
So the answer is (c) $2.4\text{ mm}$ .

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