Page 221 - Physics Coursebook 2015 (A level)

Chapter 14: Superposition of waves
10 a Explain what is meant by the term destructive interference. [2] b A student sets up an experiment to investigate the interference pattern formed by microwaves of
wavelength 1.5 cm. The apparatus is set up as in Figure 14.17 on page 199. The distance between the
centres of the two slits is 12.5 cm. The detector is centrally placed 1.2 m from the metal plates where
it detects a maximum. The student moves the detector 450 cm across the bench parallel to the plates.
Calculate how many maxima the detector will be moved through. [3]
c Calculate the frequency of these microwaves. [2]
11 a Explain what is meant by the diffraction of a wave. [2]
b Figure 14.32 shows waves, in a ripple tank, spreading out from two slits.
Figure 14.32 For End-of-chapter Question 11.
On a copy of Figure 14.32, draw:
i a line showing points along the central maximum – label this line 0 [1]
ii a line showing the points along first maximum – label this line 1 [1]
iii a line showing points along one of the first minima – label this line min. [1]
c The centres of the slits are 12 cm apart. At a distance of 60 cm from the barrier, the first maxima are
18 cm either side of the central maximum. Calculate the wavelength of the waves. You may assume
that the formula developed for light waves is applicable in this example. [3]
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