You now have two models for how light behaves: The Ray Model for Light, in which light is treated as a particle that travels in straight lines, and The Wave Model for Light, in which light is treated as an electromagnetic wave subject to superposition and interference. It turns out that both models are necessary to account for all the behavior that light exhibits, an idea known as Wave-Particle Duality
Light exhibits some properties that are wavelike, such as superposition and interference, and some properties that are particlelike, such as traveling in straight lines. Neither model on its own can account for all the properties of light!
The two models are encapsulated together by quantum mechanics, in which both light and matter is composed of fundamental particles that also exhibit wavelike behavior. A fundamental particle of light is known as a photon. The frequency of a single photon is directly related to its energy \(E = hf\text{,}\) where \(h = 6.626 \times 10^{-34}\mathrm{~Js}\) is a new fundamental constant known as Planck’s constant.
Visible light is often characterized by wavelength. For example, \(650 \mathrm{~nm}\) would be seen as red light while \(400 \mathrm{~nm}\) would be seen as purple. Given this, does a single photon of purple light have more energy, less energy, or the same energy as a single photon of red light?
A single apple contains about \(4 \times 10^6 \mathrm{~J}\) of stored energy (about \(100 \mathrm{~kCal}\)). Estimate the number of red photons that an apple tree must absorb to make one apple.
