Wave Motion — A/L Physics

What must I remember about Wave Motion?

• Wave Classification: Mechanical waves (require a physical deformable elastic medium: sound, seismic, water) vs Electromagnetic waves (can propagate across vacuum at speed c = 3 × 10⁸ m/s).
• Transverse vs Longitudinal Waves: Transverse: Particle oscillations are perpendicular to direction of wave propagation (crests and troughs; e.g., EM waves, waves on strings); Longitudinal: Particle oscillations are parallel to propagation (compressions and rarefactions; e.g., sound waves in air).
• Universal Wave Equation: v = f * λ = λ / T, where v is wave propagation speed, f is frequency (Hz), λ is wavelength (m), and T is period (s).
• Wavefront and Rays: A Wavefront is the locus of all adjacent points vibrating in identical phase; Rays are directed lines drawn perpendicular to wavefronts showing the direction of energy propagation.

Test yourself (1 minute)

1. Speed of waves in strings

   Speed of transverse wave on stretched string v = √(T / μ), where T is string tension (N) and μ is mass per unit length (kg/m).

2. Speed of sound in gases (Laplace correction)

   v = √(γ P / ρ) = √(γ R T / M); speed is independent of gas pressure P (because P/ρ remains constant at constant temperature) but increases proportionally to √T.

3. Intensity of a Wave

   Average power transmitted per unit area perpendicular to wave direction: I = P / A = (1/2) ρ v ω² A²; Intensity is proportional to square of amplitude (I ∝ A²) and square of frequency (I ∝ f²).

Practise Wave Motion questions today

Source: NIE G.C.E. (A/L) Physics Resource Book - Unit 3: Oscillations & Waves

What should I study first?

What comes next?

Next in the syllabus

Where does Wave Motion fit in the syllabus?

Unit 3.2 · Year 1 · Term 2