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4 marksProperties of Waves

CAPE Physics Unit 1 · 2014 · Paper 2 · Question 5(c)(i)

A parallel beam of sodium light is incident normally on a diffraction grating. The angle between the two first order spectra on either side of the normal is 27.7°. Assuming that the wavelength of the light is 5.89 × 10⁻⁷ m.

Find the number of rulings per mm on the grating.

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Other parts of this question

  1. 5(a)In order for waves to produce an observable interference pattern, they must be coherent. Explain what is meant by the term 'coherent' when used in this context.[1 mark]
  2. 5(b)(i)With the aid of a diagram, show that the distance, y, between the centre of the interference fringe pattern and the first bright fringe is given by y = λD/a.[5 marks]
  3. 5(b)(ii)With a pair of slits, spacing 0.20 mm, at a distance of 0.50 m from the screen, the bright fringes are 1.4 mm apart. What is the wavelength, in nm, of the…[2 marks]
  4. 5(c)(ii)Find the number of spectra obtained on either side of the normal.[3 marks]

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