Questions
1. Calculate: A wave has frequency f = 50 Hz and wavelength λ = 0.4 m. Find the unknown using v = fλ.
v = fλ = 50 × 0.4 = 20 m s⁻¹.
2. Calculate: A vibration has frequency f = 20 Hz. Find the unknown using T = 1 / f.
T = 1 / f = 1 / 20 = 0.05 s.
3. Calculate: Slits a = 0.5 mm apart, fringes x = 2.0 mm apart, screen at D = 2.0 m. Find the unknown using λ = ax / D.
λ = ax / D = (5.0 × 10⁻⁴ × 2.0 × 10⁻³) / 2.0 = 5.0 × 10⁻⁷ m.
4. Explain: how noise-cancelling headphones work.
The headphones produce a sound wave that is the exact opposite of the incoming noise. Where a crest meets a trough, the two cancel by destructive interference and the noise fades.
5. Explain: why we can hear around corners.
Sound waves spread out as they pass through openings and edges, an effect called diffraction. Because their wavelength is large, they bend around corners so you hear before you see.
6. Explain: what resonance is.
Resonance is when something is pushed at its own natural frequency, so each push adds to the last and the vibration grows large. A playground swing is the clearest example.
7. Define resonance.
The large-amplitude vibration that occurs when a system is driven at its own natural frequency.
8. Define electromagnetic spectrum.
The full range of electromagnetic waves arranged by frequency or wavelength, from radio waves to gamma rays, all travelling at the speed of light in a vacuum.
9. Define wave.
A disturbance that transfers energy from one point to another without transferring matter.
10. Define transverse wave.
A wave in which the particles of the medium vibrate at right angles to the direction the wave travels, such as water waves and light.
11. Define longitudinal wave.
A wave in which the particles of the medium vibrate parallel to the direction the wave travels, such as sound waves.
12. Define amplitude.
The maximum displacement of a vibrating particle from its equilibrium position.
Marking yourself
- Calculation: formula written, values substituted with units, final answer with unit and sensible significant figures.
- Variables: manipulated = what you change; responding = what you measure; constant = what you keep the same.
- Definition: one sentence, correct physical quantity, correct unit.
Exam tip
More Waves resources
- Chapter overview: Waves
- Revision Notes
- Common Mistakes
- Paper 2 Answering Guide
- Paper 3 Guide
- Key Terms
- Calculation practice sets
Source: DSKP KSSM Physics Form 4 and 5 (Versi English), Sijil Pelajaran Malaysia: Format Pentaksiran mulai 2021, Fizik (4531) (Bahagian Pembangunan Kurikulum (BPK), KPM)