Physics Term 2-3: Wave Properties

Study Notes

Vibrating objects transfer energy via waves, characterized by disturbances in a medium.
Energy is transferred without matter moving along with the wave.
Periodic waves repeat at regular intervals, with energy flowing outward from the vibration source.
Key features:
- Crest: high point of a wave.
- Trough: low point of a wave.
- Amplitude: maximum displacement from rest position, not the wave height.
- Wavelength (λ): distance between identical points in consecutive waves.
- Frequency (f): number of waves per second, measured in hertz (Hz). Period (T) is the time for one wave cycle; T = 1/f and f = 1/T.
- Wave speed (v) is derived from v = fλ.

Waves are classified based on energy propagation:
- Mechanical waves need a medium (e.g., sound, water).
- Electromagnetic (EM) waves have oscillating electric and magnetic fields and can propagate through a vacuum.
Mechanical waves further split into:
- Transverse waves: particle vibrations are perpendicular to energy flow (e.g., water, EM waves).
- Longitudinal waves: particles vibrate parallel to energy flow (e.g., sound waves).

Waves can be reflected from smooth or rough surfaces, illustrating scattering.
Refraction occurs when light passes through different media, bending due to speed change.
The normal is a perpendicular line to the reflection/refractive surface, determining angles of incidence (θi) and reflection (θr) with law: θi = θr.
Wavefronts represent positions of crests, with waves moving perpendicular to these fronts.

As light transitions between media (e.g., air to glass), it bends. The speed change alters the light path, akin to an axle rolling on different surfaces.
Frequency remains constant during refraction, but wavelength (λ) decreases as wave speed decreases.
Light entering denser media (e.g., glass/water) slows and bends toward the normal; exiting media speeds up and bends away.

Interference occurs when multiple waves overlap, leading to:
- Constructive interference: peak amplitudes combine, creating a greater resultant amplitude.
- Destructive interference: waves cancel each other out, producing reduced amplitude.
Standing waves develop from the interference of incident and reflected waves, forming nodes (no movement) and antinodes (maximum disturbance).

Sound is a mechanical, longitudinal wave, moving through mediums via particle vibrations.
Compressions and rarefactions visually represent sound waves.
The speed of sound in air is approximately 340 m/s and varies in different media.
Example calculation of wavelength for a sound wave at 256 Hz: λ = v/f → λ = 330/256 m = 1.29 m.
Sound waves viewed on an oscilloscope display compression and rarefaction zones.

Beats occur when two sound sources of slightly different frequencies interfere, causing rhythmic volume changes.
The Doppler Effect involves changes in frequency or pitch due to the relative motion of the sound source and observer, increasing frequency as the source approaches.