Question bank › IGCSE Physics › Waves

Properties of waves: v = fλ, f = 1/T, Doppler effect

Answer on paper first, then reveal the mark scheme one mark at a time.

1Grade 1–34 marks

The diagram shows a transverse wave on a rope.

(a) Which distance, P or Q, shows the amplitude of the wave? [1]

(b) Use the diagram to determine the wavelength of the wave. [1]

(d) Give one example of a longitudinal wave. [1]

(a) P(1)
(b) 0.40 m allow 40 cm(1)
(c) energy (and/or information) reject matter / particles / the rope / water(1)
(d) sound allow ultrasound; compression wave on a slinky / spring; P-waves (seismic)(1)
Answer: (a) P (b) 0.40 m (c) energy (d) sound
Examiner tip: Amplitude is measured from the rest position to a peak — Q (peak to trough) is twice the amplitude.

2Grade 4–53 marks

A loudspeaker produces a sound of frequency 850 Hz. The speed of sound in air is 340 m/s.

Calculate the wavelength of the sound. [3]

wave speed = frequency × wavelength or $v = f\lambda$ (in any form)(1)
$\lambda = \dfrac{340}{850}$(1)
0.40 m(1)
Answer: 0.40 m
Examiner tip: Rearrange before substituting: λ = v ÷ f. Multiplying 340 × 850 gives a nonsense answer of 289 000 m.

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