Physics Unit 11 (Waves)

Overview

This lecture covers the basics of waves, including wave parts, wave speed calculations, and the difference between transverse and longitudinal waves.

Waves transfer energy from one place to another without transferring matter.
Light and sound waves carry information that our brains interpret as images or sounds.

Displacement-distance graphs show how far a wave has traveled (distance) and how far it has oscillated from equilibrium (displacement).
Amplitude is the maximum displacement from equilibrium.
Wavelength is the distance of one complete oscillation.
Crest is the top point of the wave; trough is the bottom point.

Displacement-time graphs have time on the x-axis; one complete oscillation corresponds to the time period.
Time period is the time taken for one full oscillation.

Frequency (in hertz, Hz) is the number of oscillations per second.
Frequency = 1 / time period; time period = 1 / frequency.
For example, a time period of 0.5 s gives a frequency of 2 Hz; a frequency of 4 Hz gives a time period of 0.25 s.

Wave speed = wavelength × frequency.
Wavelength should be in meters.
Example: A wave with a 0.7 m wavelength and 400 Hz frequency has a speed of 280 m/s.

Transverse waves oscillate perpendicular to the direction of energy transfer; examples include light and water waves.
Longitudinal waves oscillate parallel to energy transfer and create compressions and rarefactions; examples include sound and seismic P waves.

Amplitude — Maximum displacement from the equilibrium position.
Wavelength — Distance of one complete wave cycle.
Crest — Highest point of a wave.
Trough — Lowest point of a wave.
Frequency (Hz) — Number of wave cycles per second.
Time period — Time taken for one complete oscillation.
Wave speed — Distance a wave travels per second (wavelength × frequency).
Transverse wave — A wave with oscillations perpendicular to energy transfer.
Longitudinal wave — A wave with oscillations parallel to energy transfer.