Describing waves — GCSE Physics practice questions

Question 1

A wave machine at one end of a leisure pool sends a steady series of waves along the pool.
A rubber duck floats in the middle of the pool. There is no wind and no current.

Which row describes the motion of the duck and what the waves transfer along the pool?

Accepted Answer

B: moves up and down about the same place · energy only. A wave transfers energy from one place to another without transferring the material it travels through. The water at each point only oscillates as the waves pass, so the duck bobs up and down about the same place while energy moves along the pool.

Question 2

A local radio station broadcasts on a frequency of 96 MHz.
Radio waves travel at 3.0 × 10⁸ m / s.

What is the wavelength of the radio waves?

Accepted Answer

C: 3.1 m. λ = v / f = 3.0 × 10⁸ / 9.6 × 10⁷ = 3.1 m.

Question 3

Four different waves each pass through an opening 1.5 m wide.

| wave | type of wave | speed | frequency |
|---|---|---|---|
| 1 | sound in air | 340 m / s | 250 Hz |
| 2 | ripples on a pond | crests travel 1.2 m in 3.0 s | 0.80 Hz |
| 3 | microwaves | 3.0 × 10⁸ m / s | 2.4 GHz |
| 4 | sound in sea water | 1500 m / s | 2.0 kHz |

Which wave spreads out the most beyond the opening?

Accepted Answer

A: wave 1. λ = v / f: wave 1, 340 / 250 = 1.4 m; wave 2, v = 1.2 / 3.0 = 0.40 m / s so λ = 0.40 / 0.80 = 0.50 m; wave 3, 3.0 × 10⁸ / 2.4 × 10⁹ = 0.125 m; wave 4, 1500 / 2000 = 0.75 m. Wave 1 has a wavelength about equal to the 1.5 m opening, so it spreads out the most; the other wavelengths are much smaller than the opening.

	motion of the duck	what the waves transfer along the pool
A	moves up and down about the same place	energy and water
B	moves up and down about the same place	energy only
C	moves along the pool with the waves	energy and water
D	moves along the pool with the waves	energy only

wave	type of wave	speed	frequency
1	sound in air	340 m / s	250 Hz
2	ripples on a pond	crests travel 1.2 m in 3.0 s	0.80 Hz
3	microwaves	3.0 × 10⁸ m / s	2.4 GHz
4	sound in sea water	1500 m / s	2.0 kHz