Features of Waves

Waves transfer energy from place to place without moving matter along with them. Examples include water waves, sound, and light.

Key Features and Terms

• Crest (peak) and trough: The highest and lowest points of a transverse wave (like water waves).
• Rest position: The middle line where the medium would be if there were no wave.
• Amplitude (A): The maximum distance from the rest position to a crest or trough. Bigger amplitude means more energy.
• Wavelength (λ): The distance between matching points on a wave, such as crest to crest or compression to compression.
• Frequency (f): How many waves pass a point each second, measured in hertz (Hz).
• Period (T): Time for one wave to pass. It links to frequency by $T = 1/f$.
• Wave speed (v): How fast the wave pattern moves: $v = f\,\lambda$.
• Wavefront: A line joining points that are in step (in phase). In a ripple tank, circular wavefronts spread out like rings.

Types of Waves (by vibration direction)

• Transverse: Vibrations are at right angles to the direction the wave travels (water waves, light, seismic S-waves).
• Longitudinal: Vibrations are parallel to the direction the wave travels (sound, seismic P-waves), made of compressions and rarefactions.

Reading Graphs

On a distance graph, measure wavelength along the horizontal axis crest-to-crest. On a time graph, measure period peak-to-peak. Amplitude is the height from rest to a crest, not crest to trough.

Real-World Links

• Sound uses longitudinal waves; higher frequency means higher pitch. Greater amplitude sounds louder.
• Water waves are mostly transverse at the surface; larger amplitude means bigger splashes.