Waves carry information — Science, 14–17 years
A wave is a repeating disturbance that can move energy and encode a signal. Frequency, wavelength and amplitude describe different features of what arrives.
Pattern, not material, travels
When one end of a rope moves up and down, the disturbance travels along the rope, but each piece of rope mainly moves around its own place. A wave carries energy and can carry a changing pattern. That pattern can become a message, sound or image.
The problem of sending signals
People needed to send information farther and faster than a person could carry it. Waves solve this by letting a source change a repeating pattern and a receiver measure those changes. Radio, light and sound use different kinds of waves, but the signalling idea is shared.
Reading a wave's frequency
A speaker produces 440 complete vibrations each second. Its frequency is therefore 440 hertz, written 440 Hz. If another sound produces 880 vibrations each second, its frequency is twice as high, so we hear a higher pitch. The loudness depends mainly on amplitude, not frequency.
Louder is not higher
It is easy to confuse a loud sound with a high sound because both can feel more intense. A loud sound has a larger amplitude, meaning the vibration is bigger. A high-pitched sound has a greater frequency, meaning more vibrations arrive each second. They are separate measurements.
Signals in communication
Mobile phones turn speech into changing electrical or radio signals, and a receiver turns the pattern back into sound. Fibre-optic internet sends information as rapid changes in light. In both cases, the message is carried by a wave pattern rather than by a stream of matter travelling from sender to receiver.
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