Nature of light
Beginner
Light behaves as both wave and particle.
Light behaves as a wave (interference, diffraction, polarisation) and as particles called photons (photoelectric effect). Which description to use depends on the situation. Light is electromagnetic radiation at 400–700 nm.
Double-slit pattern vs. single photon detection.
Light is neither a pure wave nor a tiny ball.
In more detail
Light is an electromagnetic wave that also behaves as a stream of photons. Its visible part spans wavelengths from about 380 to 750 nanometres.
Real-world uses
- Cameras, eyes and microscopes all detect light.
- Fibre optics transmit information as light pulses.
- Engineers designing a camera sensor use the particle picture of light to count photons, and the wave picture to design lenses and coatings.
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Frequently asked questions
Is light a wave or a particle?
It behaves as both, depending on the experiment, which is called wave-particle duality.
How fast does light travel?
About 3 × 10⁸ m/s in vacuum.
So is light a wave or a particle?
Both descriptions are useful. Light shows wave behaviour in interference and particle behaviour in the photoelectric effect.
Related topics in Optics
Rectilinear propagation · Reflection of light · Plane mirrors