Q1. This question is about the interference of waves. The diagram below shows an arrangement (not to scale) for observing the interference pattern produced by the superposition of two light waves.

S1 and S2 are two very narrow slits. The single slit S ensures that the light leaving the slits S1 and S2 is coherent.

(c) (i) Define coherent.

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(1)

(ii) Explain why the slits S1 and S2 need to be very narrow.

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(2)

The point O on the diagram is equidistant from S1 and S2 and there is maximum constructive interference at point P on the screen. There are no other points of maximum interference between O and P.

(d) (i) State the condition necessary for there to be maximum constructive interference at the point P.

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(1)

(ii) On the axes below, draw a graph to show the variation of intensity of light on the screen between the points O and P.

(2) (Total 6 marks)

Q2. This question is about waves and wave properties. The diagram below shows three wavefronts incident on a boundary between medium I and medium R. Wavefront CD is shown crossing the boundary. Wavefront EF is incomplete.

(a) (i) On the diagram above, draw a line to complete the wavefront EF.

(1)

(ii) Explain in which medium, I or R, the wave has the higher speed.

(3) The graph below shows the variation with time t of the velocity v of one particle of the medium through which the wave is travelling.

(b) (i) Explain how it can be deduced from the graph that the particle is oscillating.

(2) (ii) Determine the frequency of