This mini-lesson covers Themes C.2–C.5 — Wave behaviour: the wave model and v = fλ, reflection & refraction (Snell's law), diffraction & interference, standing waves & resonance, and the Doppler effect.
Work through each screen, answer the questions as you go (some are reasoning, some are calculations) and collect ⭐ stars. Watch for the HL flag on higher-level extensions. Press Start when you're ready.
A wave transfers energy without transferring matter. Two types:
Amplitude sets the energy; wavelength is the distance between adjacent in-phase points; frequency is set by the source and does not change when the wave enters a new medium.
At a boundary a wave can reflect (angle in = angle out) and refract (change direction because its speed changes). The refractive index n = c ÷ v. Snell's law links the angles:
Light travels at v = 2.0 × 10⁸ m s⁻¹ in a glass.
n = c ÷ v = 3.0 × 10⁸ ÷ 2.0 × 10⁸ = 1.5
Diffraction is the spreading of waves through a gap or around an edge — most pronounced when the gap is about one wavelength wide. When two coherent waves overlap they interfere:
Young's double-slit experiment is the classic demonstration that light is a wave: bright and dark fringes appear where light adds or cancels.
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A standing (stationary) wave forms when two identical waves travel in opposite directions (e.g. a wave and its reflection) and superpose. It has fixed nodes (no motion) and antinodes (maximum motion) — no net energy is transported.
Unlike a travelling wave, in a standing wave the nodes stay put and all points between two nodes oscillate in phase.
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The Doppler effect is the change in observed frequency when a source and observer move relative to each other. An approaching source is heard at a higher pitch (waves bunched up); a receding source at a lower pitch.
The same physics red-shifts light from galaxies moving away — key evidence for the expanding Universe. For sound it is the motion through the medium that matters.
Wave model: transfers energy not matter; v = fλ; transverse vs longitudinal
Refraction: n = c/v; Snell n₁sinθ₁ = n₂sinθ₂; slows & bends toward normal in denser medium
Interference: constructive nλ, destructive (n+½)λ; double slit s = λD/d
Standing waves: nodes & antinodes; resonance at natural frequency; no net energy transport
Doppler: approaching source → higher pitch; f' = fv/(v∓v_s)
That completes Wave Behaviour for IB Diploma Physics SL. Press Finish to see your score.
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