This module introduces the fundamental properties of waves, how they transfer energy, and their common characteristics. Understanding the correct units is crucial for describing and calculating wave phenomena.
Transverse Waves: The oscillations (vibrations) are perpendicular (at right angles) to the direction of energy transfer (wave propagation). Examples: light waves, ripples on water.
Longitudinal Waves: The oscillations (vibrations) are parallel to the direction of energy transfer (wave propagation). These waves show areas of compression (particles close together) and rarefaction (particles spread out). Example: sound waves.
Particles move up & down while the wave travels right. Adjust the sliders to explore.
Particles move left & right along the wave direction, creating compressions and rarefactions.
Adjust amplitude and wavelength to see how they change the wave shape. Labels update in real time.
Amplitude: The maximum displacement of a point on the wave from its undisturbed position (equilibrium). Larger amplitude means more energy.
Wavelength (λ): The distance between two identical points on successive waves (e.g., from crest to crest, or trough to trough). Unit: metre (m).
Frequency (f): The number of complete waves passing a certain point per second. Unit: hertz (Hz).
Period (T): The time taken for one complete wave to pass a point. Unit: second (s).
Wavefront: An imaginary line or surface connecting all points on a wave that are in the same phase of oscillation (e.g., all crests).
Waves are crucial for transferring energy and information from one place to another without transferring matter. For example, sound waves carry energy that makes your eardrums vibrate, and light waves carry information that allows you to see.
Think of a Mexican wave in a stadium. The "wave" moves around the stadium, but each person only moves up and down in their seat. The people (matter) don't travel around the stadium, but the wave (energy and the visual information of the wave) does.
Watch the pulse travel through the chain of particles. Each particle only moves up and down — energy moves right, matter does not.
The speed of a wave is related to its frequency and wavelength.
Wave Speed (v) = Frequency (f) × Wavelength (λ)
v = f × λ
Units: v in m/s, f in Hz, λ in m.
Frequency and period are reciprocals of each other.
Frequency (f) = 1 / Time Period (T)
f = 1 / T
Units: f in Hz, T in s.
These relationships apply to all types of waves, including sound waves and the various forms of electromagnetic waves (like light, radio waves, etc.).
The Doppler effect is the change in observed frequency and wavelength of a wave when the source of the wave is moving relative to an observer.
The red source moves towards the blue observer. Notice how wavefronts are compressed ahead and stretched behind.
All waves can be reflected and refracted.
Reflection: When a wave bounces off a surface. The angle of incidence equals the angle of reflection.
Refraction: When a wave changes direction as it passes from one medium to another, due to a change in wave speed. This can also cause a change in wavelength, but the frequency remains the same.
Drag the slider to change the angle of incidence. The angle of reflection always equals the angle of incidence.
1. In a transverse wave, how do the particles oscillate relative to the direction of energy transfer?
2. A wave has a frequency of 50 Hz and a wavelength of 2 m. What is its speed?
3. What is the period of a wave with a frequency of 10 Hz?
4. The Doppler effect explains why:
5. In a longitudinal wave, particles in a compression are:
6. When a wave is reflected, which property stays the same?