11.3 Light and photons
Light literally illuminates the things around us. It can be as dim and small as a faraway star on a clear night, or can be harsh and bright as the sun or the output of welding equipment. Understanding exactly the nature of light was a major research direction in physics in the nineteenth and early twentieth centuries.
The answers ended up being far more complicated than anyone imagined, gave birth to quantum mechanics, and involved the electromagnetic spectrum well beyond visible light.
11.3.1 Photons
Does light behave like a wave, with varying amplitude A (height) and frequency ν? The wavelength λ is the distance between two wave crests or other corresponding points. (λ is the Greek letter ‘‘lambda’’ and ν is the Greek letter ‘‘nu’’.)
Or does light behave like a particle with a well-defined shape, shooting off in various directions...
