Beginner · 10 min
Waves and sound
Connect wavelength, frequency, wave speed, and the time for one cycle.
How a wave repeats
Waves transfer energy. Sound travels through a material as a repeating disturbance in pressure; it cannot travel through a vacuum. Wavelength is the distance between matching points on neighbouring cycles. Frequency is the number of cycles per second, measured in hertz (Hz). For a repeating wave, wave speed equals frequency multiplied by wavelength: v = f × λ. Speed depends on the wave and the medium.
Worked example
A wave has a frequency of 3 Hz and a wavelength of 2 m. Wave speed = 3 × 2 = 6 m/s
The time for one cycle
The period is the time taken for one complete cycle. Period and frequency are reciprocals: T = 1 ÷ f. A higher frequency means more cycles each second and a shorter period. For sound, frequency is closely related to pitch. Loudness is related to the size of the pressure disturbance, not simply to how many cycles occur each second.
Worked example
A repeating wave has a frequency of 2 Hz. Period = 1 ÷ 2 = 0.5 s
Sketch a repeating wave
- Draw two matching wave cycles. Mark one wavelength between matching points.
- Compare the periods of waves with frequencies of 2 Hz and 5 Hz. Identify which repeats more often each second.