O-LevelPhysicsWaves5054/21 · May/June 2023 · Q77 Marks

A water wave in a ripple tank diffracts as it passes through the gap in a barrier. Fig. 7.1 shows a drawing made by a student of the crests in the pattern. [Figure 7.1]

(a)State one way in which the student's drawing of the crests is wrong.[1]
(b)The gap in the barrier is now made smaller than the wavelength, as shown in Fig. 7.2. Complete Fig. 7.2 with at least three crests to show the new diffraction pattern.[2]
(c)(i)Define the term 'wavelength'.[1]
(c)(ii)Calculate the frequency of the wave.[2]
(c)(iii)Calculate the wavelength of the wave in the shallow part of the tank.[1]

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Mark scheme

Marking points from the official mark scheme (May/June 2023). The mark or mark type is shown in brackets.

[B1] wavelength has altered / too large or crests in shadow should be bent / quarter circular above or below gap or vertical lines too straight on two crests
[B1] at least 3 semicircles centered on the gap
[B1] wavelength constant and the same on right and left of gap and some bending
[B1] distance between two (consecutive) identical points such as two (consecutive) crests
[C1] v = fλ numerical or algebraic e.g. f = 6 / 2 (Hz)
[A1] 3(.0) Hz)
[B1] 1.3 (cm)

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