Waves are vibrations that transfer energy from place to place.
In transverse waves, the oscillations (vibrations) are at right angles to the direction of travel and energy transfer
Light and other types of electromagnetic radiation are transverse waves.
In longitudinal waves, the oscillations are along the same direction as the direction of travel and energy transfer.
Sound waves and waves in a stretched spring are longitudinal waves.
Amplitude, Wavelength and Frequency
As waves travel, they set up patterns of disturbance. The amplitude of a wave is its maximum disturbance from its undisturbed position.
The wavelength of a wave is the distance between a point on one wave and the same point on the next wave. It is often easiest to measure this from the crest of one wave to the crest of the next wave
The frequency of a wave is the number of waves produced by a source each second. It is also the number of waves that pass a certain point each second.
The unit of frequency is the hertz (Hz).
Refraction and Reflection
Sound waves and light waves change speed when they pass across the boundary between two substances with different densities, such as air and glass.There is one special case you need to know. Refraction doesn't happen if the waves cross the boundary at an angle of 90° (called the normal) - in that case they carry straight on.
When waves reflect they follow the law of reflection:
the angle of incidence equals the angle of reflection
- The normal is a line drawn at right angles to the reflector
- The angle of incidence is between the incident (incoming) ray and the normal
- The angle of reflection is between the reflected ray and the normal.
Speed Of A Wave
The speed of a wave is related to its frequency and wavelength, according to this equation:
v = f × λ
- v is the wave speed in metres per second, m/s
- f is the frequency in hertz, Hz
- λ (lambda) is the wavelength in metres, m.