Waves are produced by oscillating or vibrating systems, and transfer energy without transferring matter. (p.172)
Progressive wave: the wave profile moves (propagates) with time. Stationary wave: the wave profile does not propagate (produced by two identical progressive waves moving in opposite directions). (p.174)
Mechanical wave requires a medium (e.g. water, sound, seismic waves). Electromagnetic wave needs no medium and is made of oscillating electric and magnetic fields perpendicular to each other (e.g. radio waves, light, gamma rays). (p.175)
Transverse wave: particle vibration is perpendicular to the direction of propagation; has crests and troughs. Longitudinal wave: particle vibration is parallel to the direction of propagation; has compressions and rarefactions. (p.177)
Definitions: Amplitude (A), Period (T), Frequency (f = 1/T), Wavelength (λ), Wave speed (v). (p.178)
Wave speed, v = fλ (p.179)
5.2 Damping and Resonance
Damping is the reduction in amplitude of an oscillating system over time due to loss of energy. External damping: friction/air resistance. Internal damping: stretching and compression of particles. (p.184)
During damping, oscillation frequency stays constant while amplitude decreases. (p.185)
Resonance occurs when a periodic force is applied to a system at its natural frequency, causing it to oscillate with maximum amplitude. (p.186)
Real-world resonance examples: Tacoma Narrows Bridge collapse (1940), London Millennium Footbridge oscillations, tuning of musical instruments. (p.187)
5.3 Reflection of Waves
A wavefront is a line joining points that are in phase. (p.188)
Depth sounding with ultrasonic waves: distance travelled = speed × time; for the round trip to the seabed and back, 2d = vt. (p.193)
5.4 Refraction of Waves
Refraction of waves is a change in the direction of wave propagation caused by a change in wave velocity as the wave moves between media. (p.194)
Deep → shallow water: angle of incidence > angle of refraction; wavelength decreases; speed decreases; frequency unchanged; wave bends towards the normal. Shallow → deep water: opposite effects; wave bends away from the normal. (p.196)
v1/λ1 = v2/λ2 (frequency remains constant across the boundary). (p.199)
5.5 Diffraction of Waves
Diffraction is the spreading of waves as they pass through a slit or around the edge of a barrier. (p.202)
Effects of diffraction: wavelength, frequency and speed are unchanged; amplitude decreases; direction of propagation spreads into many directions. (p.205)
Diffraction is more significant with a narrow slit or long wavelength, and less significant with a wide slit or short wavelength. (p.208)
5.6 Interference of Waves
Interference is the superposition of two or more coherent waves (same frequency, constant phase difference). (p.211)
Young's double-slit experiment: bright fringes form by constructive interference; dark fringes form by destructive interference. (p.214)
λ = ax/D, where a = distance between two coherent sources, x = distance between adjacent antinodal/nodal lines, D = perpendicular distance from the sources to the measurement point. (p.217)
Electromagnetic waves consist of oscillating electric (E) and magnetic (B) fields, perpendicular to each other and to the direction of propagation. (p.220)
Properties: transverse waves; no medium required; speed in vacuum c = 3.00 × 108 m s−1; exhibit reflection, refraction, diffraction and interference. (p.221)
Electromagnetic spectrum (increasing frequency, decreasing wavelength): Radio waves → Microwave → Infrared → Visible light → Ultraviolet → X-ray → Gamma ray. Energy carried is directly proportional to frequency. (p.221)