Light as a wave but not a particle
A prism demonstrates light is a wave not a particle called a photon.
A photon is the quantum particle for a wavelength of light.
When treating light as a particle, a prism spreading light into a rainbow is awkward to explain.
Each color would be a photon for each wavelength.
When the white light passes through the prism at an angle the wavelengths are spread out uniformly.
This spread results from the diffraction index of the medium. The glass is at an angle and the triangular shape has a uniform slope for a corresponding slope of the changing diffraction.
If light is treated as a particle this observed behavior is harder to explain.
As individual particles, each photon will slow down at their individual different rates due to the changing diffraction in the medium during their path.
Each photon should maintain its straight path but should arrive at slightly different times. The result would be white.
Only light as a wave propagating in a medium can all the wavelengths change their path into the observed rainbow.
As individual photons there must be a force (or something?) maintaining their coordination with the other photons in the spread of the rainbow.
I discovered a concept called a quantum rainbow where one photon has the range of colors. The site proposing a quantum rainbow is just an informal explanation with a cartoon.
The use of photon can bother me because it dispenses with light as the propagation of synchronized electric and magnetic fields. Instead light is considered quantized particles. That can be a misleading interpretation of light.
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