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JEE Main 2021 (31 Aug, Shift 2) · YDSE: Fringe Width & Fringe Positions

YDSE: Fringe Width & Fringe Positions question from JEE Main 2021 (31 Aug, Shift 2)

Q58JEE Main 2021 · 31 AUG · SHIFT 2Medium

YDSE: Fringe Width & Fringe Positions

In a Young's double slit experiment, the slits are separated by 0.3 mm and the screen is 1.5 m away from the plane of slits. Distance between fourth bright fringes on both sides of central bright is 2.4 cm. The frequency of light used is ______________ ×\times 1014 Hz.

Numerical answer type. Work it out, then open the answer.

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Answer: 5

  1. Distance between 4th bright fringes on both sides =8β=2.4= 8\beta = 2.4 cm, so β=0.3 cm=3×10−3\beta = 0.3\text{ cm} = 3\times10^{-3} m.
  2. λ=βdD=3×10−3×0.3×10−31.5=6×10−7\lambda = \frac{\beta d}{D} = \frac{3\times10^{-3}\times0.3\times10^{-3}}{1.5} = 6\times10^{-7} m
  3. f=cλ=3×1086×10−7=5×1014f = \frac{c}{\lambda} = \frac{3\times10^{8}}{6\times10^{-7}} = 5\times10^{14} Hz
  4. So the answer is 5.
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