The questions are on the wave speed test. Take it under real conditions before reading the mark scheme.
Quick answer: A wave carries energy without carrying matter. This mark scheme gives the model answers and the marks for the 8 questions of the Physics 9-10 test on wave speed, from two types of wave to unchanged quantity, with the equivalent answers to accept.
Mark as shown. Accept answers that are worded differently but scientifically equivalent. Apply follow-through where an earlier error is carried into a later calculation, 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: HS-PS4-1, GCSE P6
Question 1 Two types of wave (2 marks)
- A wave in which the vibrations are at right angles to the direction of travel of the wave (energy).
- Sound, a compression wave on a slinky, or a P-wave in an earthquake.
Marking: 1 mark each part.
Question 2 Wave speed (3 marks)
v = f λ = 12 × 0.35 = 4.2 m/s.Marking: equation (1), substitution (1), answer with unit (1).
Question 3 Wave on a spring (4 marks)
- 4 cm.
- 20 cm.
- f = v / λ = 40 / 20 = 2.0 Hz.
- T = 1 / f = 1 / 2.0 = 0.50 s.
Marking: 1 mark each part.
Question 4 Moving into shallow water (3 marks)
(a) The speed decreases. (b) The wavelength decreases. (c) The frequency does not change.Marking: 1 mark each.
Question 5 Reflection angle (3 marks)
The wavefront is at 25° to the barrier, so the ray meets the normal at 90° − 25° = 65°. Angle of incidence = 65°. By the law of reflection, angle of reflection = 65°. The law: angle of incidence = angle of reflection.Marking: 65° (1); 65° (1); law stated (1).
Question 6 Diffraction (2 marks)
The waves spread out strongly (diffract) after a gap of about one wavelength. A gap ten times as wide gives little spreading because the gap is much larger than the wavelength.Marking: strong spreading for 2 cm gap (1); little spreading for 20 cm gap because gap much greater than λ (1).
Question 7 Counting waves (2 marks)
T = 1 / 0.20 = 5.0 s. In 60 s the number of waves is 60 × 0.20 = 12 waves.Marking: period (1); number of waves (1).
Question 8 Unchanged quantity (1 mark)
The frequency.Marking: 1 mark.
