Microwaves with the same wavelength and amplitude are emitted in phase from two sources X and Y, as shown in Fig. 5.1. [Figure 5.1] A microwave detector is moved along a path parallel to the line joining X and Y. An interference pattern is detected. A central intensity maximum is located at point A and there is an adjacent intensity minimum at point B. The microwaves have a wavelength of 0.040 m.

1. (a)Calculate the frequency, in GHz, of the microwaves. frequency = .............................................. GHz[3]
2. (b)(i)For the waves arriving at point B, determine: the path difference path difference = .............................................. m[1]
3. (b)(ii)the phase difference. phase difference = .............................................. .°[1]
4. (c)The amplitudes of the waves from the sources are changed. This causes a change in the amplitude of the waves arriving at point A. At this point, the amplitude of the wave arriving from source X is doubled and the amplitude of the wave arriving from source Y is also doubled. Describe the effect, if any, on the intensity of the central maximum at point A.[2]
5. (d)(i)Describe the effect, if any, on the positions of the central intensity maximum and the adjacent intensity minimum due to the following separate changes. The separation of the sources X and Y is increased.[1]
6. (d)(ii)The phase difference between the microwaves emitted by the sources X and Y changes to 180°.[1]

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