JEE Main 2017 · 8 Apr · Shift 1 · Physics Q23

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PhysicsSingle correct+4 / -1Question 23 of 90

A single slit of width b is illuminated by a coherent monochromatic light of wavelength λ. If the second and fourth minima in the diffraction pattern at a distance 1 m from the slit are at 3 cm and 6 cm respectively from the central maximum, what is the width of the central maximum ? (i.e. distance between first minimum on either side of the central maximum)

1.5 cm

3.0 cm

4.5 cm

6.0 cm

Answer and worked solution

Official answer: B

Minima are at $y_n=\dfrac{n\lambda D}b$ . The second minimum at 3 cm gives $\dfrac{\lambda D}b=1.5$ cm (the fourth, at 6 cm, agrees). The central maximum is $2\times1.5=3.0$ cm wide.

Topics:Diffraction

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JEE Main 2017 · 8 Apr · Shift 1, Physics question 23