JEE Main · 2022 · 26 Jul 2022 · Shift 1 · Wave Optics

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In young's double slit experiment, the fringe width is 12 mm. If the entire arrangement is placed in water of refractive index

\frac{4}{3}

, then the fringe width becomes (in mm)

(A)16
(B)9✓ Correct
(C)48
(D)12

Answer: (B)

Solution

Fringe width

β = \frac{λ D}{d}

.

When the setup is placed in a medium of refractive index

μ

, the effective wavelength becomes

λ_{med} = \frac{λ}{μ}

.

Therefore,

β_{med} = \frac{β _{vacuum}}{μ} = \frac{12}{4/3} = 12 \times \frac{3}{4} = 9 mm

JEE Main · 2022 · 26 Jul 2022 · Shift 1 · Single correct option

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