Waves: Paper 2 Answering Guide (Form 4 SPM Physics)

Paper 2 at a glance

• Paper 2 lasts 2 hours 30 minutes

"Define" items from this chapter

One precise sentence each; the unit is part of the definition where there is one.

• 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.
• Longitudinal wave, A wave in which the particles of the medium vibrate parallel to the direction the wave travels, such as sound waves.
• Amplitude, The maximum displacement of a vibrating particle from its equilibrium position.
• Wavelength, The distance between two successive points in phase on a wave, such as two neighbouring crests; measured in metres (m).
• Frequency, The number of complete oscillations or waves produced in one second; measured in hertz (Hz).
• Period, The time taken to complete one full oscillation or one complete wave; measured in seconds (s).

"Explain" items from this chapter

Give the physics reason, not a description. Model answers in one breath:

• 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.
• 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.
• 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.

"Calculate" items from this chapter

Formula, substitution with units, answer with unit, and the trap examiners set for each one.

• v = fλ, Wave speed, v = wave speed (m s⁻¹); f = frequency (Hz); λ = wavelength (m) · Convert the wavelength to metres (from cm or mm) and keep frequency in hertz.
• T = 1 / f, Period and frequency, T = period (s); f = frequency (Hz) · Period and frequency are reciprocals: T in seconds, f in hertz. Do not confuse the two.
• λ = ax / D, Interference of waves, λ = wavelength (m); a = slit separation (m); x = fringe separation (m); D = distance from slits to screen (m) · Do not swap a (slit separation) with x (fringe separation). Convert all distances to metres before substituting.

Other command words

• Suggest / Modify (Section C), one modification, one reason, tied to a named physics principle; repeat for each aspect the question lists.
• Describe, say what happens, in order, with the observable evidence; keep "why" for an explain mark.

Where the marks are in this chapter

The 7 content standards of Waves can each be asked as a definition, an explanation, a calculation or a diagram. We do not predict which will appear, prepare all of them.

• 5.1 Fundamentals of Waves
• 5.2 Damping and Resonance
• 5.3 Reflection of Waves
• 5.4 Refraction of Waves
• 5.5 Diffraction of Waves
• 5.6 Interference of Waves
• 5.7 Electromagnetic Waves

A three-step answer routine

1. Underline the command word and the quantity asked for.
2. Write the principle or formula before any numbers.
3. Close with the unit, the direction (if a vector) and a one-line conclusion.

More Waves resources

• Chapter overview: Waves
• Revision Notes
• Common Mistakes
• Practice Questions
• 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)