Wave Physics
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About this area
Lenses and sensors both depend on the wave nature of light. This area explains interference, how light behaves inside glass, and how the sensor sets a second limit on resolution.
Read interference first, because it underpins coatings and diffraction. The propagation article then covers what happens inside glass, and the sensor article links the optics to the pixels that record the image.
Going further
From waves to images: light is an electromagnetic wave, and every optical effect in a lens can be traced to that wave nature. Interference explains coatings and fringes. Propagation through glass explains refraction and dispersion. Sampling by a sensor explains the final limit on detail.
Articles in this area
- Constructive and Destructive Interference: How waves add and cancel, and why it matters for coatings and diffraction.
- Light Propagation Through Glass: Speed, wavelength and direction of light inside a medium.
- Sensor Pitch and Resolving Power: How pixel spacing limits the detail a camera can record.
Where to go next
Return to the pillar guide to see how this area connects to the others.
Why the wave description matters
Much of optics can be treated with rays, but some effects cannot. Coatings depend on interference, which needs the wave description. Diffraction, which sets the limit of resolution, is also a wave effect. The sensor limit is different: it comes from sampling, which the wave description supports but does not define. This area gives the wave background that the other two areas use.
The three articles follow a logical order. Interference introduces phase and path difference. Propagation through glass applies the same ideas to refraction and dispersion. The sensor article connects the optics to the pixels that record the image.
Questions this area answers
Why do anti-reflection coatings look coloured? Their cancellation depends on wavelength, so the residual reflected colour shows where the coating works least well.
Why does glass separate colours? Its refractive index varies with wavelength, so each colour is bent by a slightly different amount at each surface.
Why is there a limit on detail from the sensor? A sensor samples the image at a fixed spacing, and detail finer than half that spacing cannot be recorded correctly.
Limits of this area
These articles give the physical principles and simple calculations. They do not replace a full treatment of electromagnetic theory, and they do not describe the detailed design of any coating or sensor. For those, the textbooks listed in the sources are the right next step.
A simple experiment to try
Look at a thin oil film on water in daylight. The bright colours come from interference between light reflected from the top and bottom surfaces of the film. As the film thins, the colours change, because the path difference changes. The same principle, applied with more precise films, makes anti-reflection coatings work.
General information only. This page explains optical principles and does not replace lens design work, lens testing or advice from a qualified optical engineer.