Physics › Section S · Vision, instruments, and wave optics › Topic S.6
Thin-film interference
The swirling colours of a soap bubble and the rainbow sheen of oil on a wet road come from light reflecting off the two faces of a very thin layer. The same physics, run in reverse, lets engineers coat lenses and solar cells so that they hardly reflect at all.
In this topic
- Colours from a layer thinner than a hair
- The extra path inside the film
- The half-wavelength phase change on reflection
- Putting the two effects together
- Worked example: a soap film in white light
- Oil on water
- Worked example: the thinnest bright oil film
- Anti-reflection coatings
- Worked example: coating a solar cell
- Common mistakes to avoid
- Key takeaways
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