Waves: transverse, longitudinal and v = f λ
Wave types, key words and the wave equation.
Two types of wave
Transverse waves oscillate at right angles to the direction the energy travels (light, water ripples, all EM waves). Longitudinal waves oscillate parallel to the direction of travel, with compressions and rarefactions (sound).
Key words
Amplitude: maximum displacement from rest. Wavelength (λ): distance from one point to the same point on the next wave. Frequency (f): number of waves per second, in hertz (Hz).
The wave equation
wave speed = frequency × wavelength, v = f × λ.
✏️ Worked example
A sound wave has frequency 170 Hz and wavelength 2 m. What is its speed?
v = f × λ = 170 × 2 = 340 m/s.
🧠 Test yourself
Is sound transverse or longitudinal?
Longitudinal.
What is the unit of frequency?
Hertz (Hz).
A wave travels at 3 m/s with wavelength 0.5 m. Frequency?
f = 3 ÷ 0.5 = 6 Hz.
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