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Refraction, diffraction and interference

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Question 2

A researcher is calibrating a double-slit interferometer for a high-precision optical sensor. In the initial configuration, a light source of wavelength λ \lambda\,λ passes through two slits separated by a distance sss, with a detector array placed at a distance D D\,D behind the slits. This setup produces an interference pattern with a fringe spacing of www.

Due to temperature variations and realignment:

  • The wavelength of the source is decreased to 0.90λ0.90\lambda0.90λ.
  • Thermal expansion increases the slit separation to 1.20s.
  • The distance between the slits and the detector array is adjusted to 1.60D 1.60D\,1.60D to maintain focus.

What is the new fringe spacing w′ w'\,w′ at the detector array in terms of the original spacing www?

A

0.68w0.68w0.68w

B

0.75w0.75w0.75w

C

1.20w1.20w1.20w

D

1.73w1.73w1.73w

Markscheme

Refraction, diffraction and interference Questions

  1. A Level
  2. /Physics
  3. /Refraction, diffraction and interference

37 exam-style questions on AQA A Level Physics Refraction, diffraction and interference, covering Interference, Diffraction, and Refraction at a plane surface. Each one has a worked solution and a mark scheme showing where the marks go.

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