A-LevelPhysicsWaves9702/42 · May/June 2018 · Q57 Marks

In radio communication, the bandwidth of an FM transmission is greater than the bandwidth of an AM transmission. State what is meant by bandwidth,

(a)(i)In radio communication, the bandwidth of an FM transmission is greater than the bandwidth of an AM transmission. State what is meant by bandwidth,[1]
(a)(ii)one advantage and one disadvantage of a greater bandwidth.[2]
(b)(i)A carrier wave has a frequency of 650 kHz and is measured to have an amplitude of 5.0 V. The carrier wave is frequency modulated by a signal of frequency 10 kHz and amplitude 3.0 V. The frequency deviation of the carrier wave is 8.0 kHz V⁻¹. Determine, for the frequency modulated carrier wave, the measured amplitude,[1]
(b)(ii)the maximum and the minimum frequencies,[2]
(b)(iii)the minimum time between a maximum and a minimum transmitted frequency.[1]

Mark scheme

Marking points from the official mark scheme (May/June 2018). The mark or mark type is shown in brackets.

[B1] range of frequencies (of signal)
[B1] advantage: e.g. better quality (of reproduction) greater rate of transfer of data less distortion
[B1] disadvantage: e.g. fewer stations (in any frequency range)
[A1] 5.0 V
[A1] maximum: 674 kHz
[A1] minimum: 626 kHz
[A1] T = 1 / (10 × 10³) = 1.0 × 10⁻⁴ s
minimum time = T/2
= 5.0 × 10⁻⁵ s

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