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In producing a pure spectrum , the incident light is passed through a narrow slit placed in the focal plane of an achromatic lens because a narrow slit allows only one colour at a time , produces less diffraction , increases intensity , allows a more parallel beam when it passes through the lens

  •  In producing a pure spectrum , the incident light is passed through a narrow slit placed in the focal plane of an achromatic lens because a narrow slit
  • allows only one colour at a time ,
  • produces less diffraction ,
  • increases intensity ,
  • allows a more parallel beam when it passes through the lens 

Grade:8

1 Answers

Saurabh Koranglekar
askIITians Faculty 10335 Points
4 years ago
If the slit is wide, different part of the slit produces different spectra, which overlap resulting in impure spectrum. Therefore narrow slit is used as it allows more parallel beam of light when it passes through the lens.

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