Electromagnetic Radiation
Quantum and Nuclear | Light, Sound and Waves

Vibrating - radiating - absorbing

Physics Narrative for 14-16 Supporting Physics Teaching

A vibration is mimicked elsewhere: its amplitude and frequency are copied, but with a time delay

Something vibrates. Later, somewhere else, something else mimics that vibration. The two objects are linked somehow. A wave theory is one way to provide an account of the links between the two. A wave is just a whole chain of things, vibrating one after the other. In the SPT: Sound topic and the SPT: Light topic lots of phenomena were presented, and some work done on vibrations and what a time trace of the vibrations might look like. For sound it was rather easy to imagine a whole chain of links between source and detector, in light rather less easy. In this episode, you've made a much more thorough and rigorous study of the connections between source and absorber, rather than just asserting It's a wave. You've been restricted to a single beam: that'll change in episode 03. You've also been restricted to a pre-1900 view: that'll change in episode 02.

The central ideas:

Everything that vibrates, or oscillates, has a frequency and an amplitude.

Many vibrations are propagated from the source, often at a characteristic family speed, to their eventual terminus at an absorber. This is called radiating.

Such radiating can be a way of shifting energy from the source to the absorber: the heating by radiation pathway.

Some absorbers can function as detectors, because there is some change that we can interpret as the arrival of radiation.

Rays can be used to predict beams.

The behaviour of optical devices (lenses and prisms; mirrors, both plane and curved) can be accounted for using rules about rays.

Careful thinking about steadily changing trip times and frequency accounts for the Doppler effect.

Waves can be modulated (frequency or amplitude) to carry a signal, and so information.

Extension ideas:

Considering many paths, and looking for a minimum in trip time, allows you to predict the rays.

Limit Less Campaign

Support our manifesto for change

The IOP wants to support young people to fulfil their potential by doing physics. Please sign the manifesto today so that we can show our politicians there is widespread support for improving equity and inclusion across the education sector.

Sign today