This question is about investigations involving an electromagnetic wave.
A vertical transmitter aerial emits a vertically polarised electromagnetic wave which travels towards a vertical receiver aerial. The wavelength of the wave is 0.60 m.
Fig. 5.1 shows a short section of the oscillating electric field of the electromagnetic wave.
Fig. 5.1
Calculate the frequency f of the transmitted wave.
f = ...................................... Hz
Suggest why the diode in Fig. 5.1 is necessary for an ammeter to detect a signal at the receiver aerial.
A student carries out two investigations with these electromagnetic waves.
In investigation 1, the student rotates the receiver aerial about the horizontal axis joining the two aerials, as shown in Fig. 5.1.
In investigation 2, the student places a metal sheet behind the receiver aerial. The student moves the sheet backwards and forwards along the horizontal axis joining the two aerials, as shown in Fig. 5.2.
Fig. 5.2
For each of these two investigations:
Explain why the ammeter sometimes gives a maximum reading and sometimes a zero (or near zero) reading.
State the orientations of the receiver aerial in investigation 1, and the positions of the metal sheet in investigation 2, where these maximum and zero readings would occur.
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