Wave behaviour — Physics, 14–17 years
How vibrations carry energy and interact through reflection, refraction, and interference.
The idea
A wave is a repeating disturbance that transfers energy without carrying the material along overall. Its frequency is how often it repeats each second, its wavelength is the distance between matching points, and its amplitude measures the size of the disturbance. Wave speed follows v = fλ.
Why we need it
Ripples, sound, light, and earthquake signals look different, but the same wave ideas reveal patterns in all of them. Scientists needed a way to describe energy travelling through water, air, solids, or empty space. This framework explains why waves bounce, bend, spread, and sometimes reinforce or cancel one another.
Worked example
A sound wave has frequency 500 Hz and wavelength 0.68 m. Use v = fλ, so v = 500 × 0.68 = 340 m/s. If the frequency rises to 1000 Hz while the sound stays in the same air, the speed remains about 340 m/s, so the wavelength becomes 340 ÷ 1000 = 0.34 m.
The common trap
A common mistake is saying that a louder sound travels faster than a quiet one. It feels plausible because a loud disturbance has a larger amplitude, and amplitude looks like “more” of the wave. In the same medium, amplitude changes the energy carried, while frequency changes pitch; wave speed is mainly set by the medium.
Where it appears
Noise-cancelling headphones create a second sound wave that interferes destructively with unwanted noise. Glasses and lenses use refraction to bend light and form useful images. Radio, mobile networks, ultrasound scans, sonar, and earthquake monitoring all measure or send waves, using their frequency, timing, or direction.
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