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5 marksProperties of Waves

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

A laser beam is incident on two narrow slits separated by a distance, a. The slits are at a distance, D, from a screen.

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.

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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)(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]
  3. 5(c)(i)Find the number of rulings per mm on the grating.[4 marks]
  4. 5(c)(ii)Find the number of spectra obtained on either side of the normal.[3 marks]

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