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NEET 1991 (AIPMT) · YDSE: Fringe Width & Fringe Positions

YDSE: Fringe Width & Fringe Positions question from NEET 1991 (AIPMT)

Q77NEET 1991 · AIPMTMedium

YDSE: Fringe Width & Fringe Positions

In Young's experiment, two coherent sources are placed 0.90 mm apart and fringe are observed one metre away. If it produces second dark fringe at a distance of 1 mm from central fringe, the wavelength of monochromatic light used would be

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Answer: (d)

  1. 2nd dark fringe: y=1.5β=1y = 1.5\beta = 1 mm, so β=23\beta = \frac{2}{3} mm
  2. λ=βdD=(2/3)×10−3×0.9×10−31=6×10−7 m\lambda = \frac{\beta d}{D} = \frac{(2/3)\times10^{-3} \times 0.9\times10^{-3}}{1} = 6\times10^{-7}\text{ m}
  3. So the answer is (d) 6×10−56\times10^{-5} cm.
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