Properties of Waves
4 marks · EasyA ripple tank is used to demonstrate water waves. The table below shows the number of waves passing a fixed point in different time intervals.
| Interval (s) | Number of waves |
|---|---|
| 10 | 25 |
| 10 | 30 |
Calculate the frequency of the waves in the first experiment (25 waves in 10 seconds).
State the definition of frequency.
If the wavelength of these water waves is measured to be 0.048 m, calculate the wave speed for the first experiment.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) f = 2.5 Hz · must show Uses f = Number of waves / time
(b) Frequency is the number of waves passing a point per second. · must show definition: number of waves per second
(c) v = 2.5 × 0.048 = 0.12 m/s · must show Correct use of v = f × λ, Correct substitution and answer
Common mistakes: Incorrect use of frequency formula; Incorrect substitution in speed formula
Show mark scheme and worked solution
Marking points
A1 (a) · 1 mark · Correct frequency (2.5 Hz) with working.
B1 (b) · 1 mark · Correct definition of frequency (waves per second).
M1 (c) · 1 mark · Correct substitution into v = f × λ.
A2 (c) · 1 mark · Correct value for wave speed: 0.12 m/s. (follow-through)
Worked solution
a) Frequency, f = Number of waves / Time = 25/10 = 2.5 Hz
b) Frequency is the number of waves passing a fixed point per second.
c) v = 2.5 \times 0.048 = 0.12 m/s