The questions are on the sound waves test. Take it under real conditions before reading the mark scheme.
Quick answer: Sound is a longitudinal wave of compressions and rarefactions that needs a medium to travel through. This mark scheme gives the model answers and the marks for the 8 questions of the Physics 9-10 test on sound waves, from hearing range to speed in air, with the equivalent answers to accept.
Mark as indicated. Accept equivalent wording and allow follow-through from earlier errors. Penalise a missing unit only once in the whole paper, and do not penalise sensible rounding to 2 or 3 significant figures.
Level: Physics grades 9-10 (GCSE · IGCSE · O Level · Class 9-10) · Curriculum: IGCSE 3.4
Question 1 Hearing range (2 marks)
- About 20 Hz to 20 000 Hz (20 kHz).
- Sound with a frequency higher than the upper limit of human hearing, above 20 kHz.
Marking: 1 mark each part.
Question 2 Thunder (3 marks)
d = v t = 330 × 6.0 = 1980 m = 2.0 km (1.98 km).Marking: equation (1), substitution (1), answer with unit (1).
Question 3 Sonar (3 marks)
d = v t / 2 = 1500 × 0.160 / 2 = 120 m.Marking: total distance 240 m (1); halving (1); answer with unit (1).
Question 4 Two sounds (4 marks)
- Trace Y (more waves in the same time).
- Trace X (larger amplitude).
- X has two waves in 10 ms, so T = 5.0 ms = 0.0050 s and f = 1 / 0.0050 = 200 Hz.
- λ = v / f = 330 / 200 = 1.65 m.
Marking: 1 mark each part.
Question 5 Sound in air (3 marks)
The loudspeaker cone vibrates and pushes on the air particles, creating regions of compression and rarefaction. These pass along as a longitudinal wave, each particle vibrating to and fro in the direction of travel and passing the energy on. The energy reaches the ear, but the particles do not travel.Marking: vibrating source / compressions and rarefactions (1); longitudinal, parallel vibration (1); energy transferred, not particles (1).
Question 6 Sound and vacuum (2 marks)
A sound wave is passed from particle to particle. A vacuum has no particles, so there is nothing to carry the vibrations.Marking: sound needs particles to pass vibrations (1); vacuum has none (1).
Question 7 Medical ultrasound (2 marks)
Pulses of ultrasound are sent into the body and are partly reflected at the boundaries between different tissues. A detector records the time for each echo, and a computer uses the time to calculate the depth and builds up an image.Marking: reflection at boundaries (1); time of echo gives depth / image built by computer (1).
Question 8 Speed in air (1 mark)
330 m/s (accept values between 330 and 343 m/s).Marking: 1 mark.
