Photon energy - Wikipedia
electromagnetic radiation with shorter wavelengths is more energetic. The relation- ship between energy and frequency is given by the equation, E = hν, where h. Photon energy is the energy carried by a single photon. The amount of energy is directly proportional to the photon's electromagnetic frequency and inversely proportional to the wavelength. The higher the photon's frequency, the higher its energy. where f is frequency, the photon energy equation can be simplified to. The energy of a photon could be calculated using Planck's equation: . The relationship between photoelectron kinetic energy and light frequency is shown in.
The dock represents a metal surface, the beach balls represent electrons, and the ocean waves represent light waves. If a single large wave were to shake the dock, we would expect the energy from the big wave would send the beach balls flying off the dock with much more kinetic energy compared to a single, small wave.
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This is also what physicists believed would happen if the light intensity was increased. Light amplitude was expected to be proportional to the light energy, so higher amplitude light was predicted to result in photoelectrons with more kinetic energy.
Classical physicists also predicted that increasing the frequency of light waves at a constant amplitude would increase the rate of electrons being ejected, and thus increase the measured electric current. Using our beach ball analogy, we would expect waves hitting the dock more frequently would result in more beach balls being knocked off the dock compared to the same sized waves hitting the dock less often. Now that we know what physicists thought would happen, let's look at what they actually observed experimentally!
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When experiments were performed to look at the effect of light amplitude and frequency, the following results were observed: The kinetic energy of photoelectrons increases with light frequency. Electric current remains constant as light frequency increases.
Electric current increases with light amplitude. The kinetic energy of photoelectrons remains constant as light amplitude increases. These results were completely at odds with the predictions based on the classical description of light as a wave! In order to explain what was happening, it turned out that an entirely new model of light was needed.
That model was developed by Albert Einstein, who proposed that light sometimes behaved as particles of electromagnetic energy which we now call photons.
There are two equations concerning light that are usually taught in high school. Typically, both are taught without any derivation as to why they are the way they are. That is what I will do in the following. It is well-known who first wrote this equation and when it happened.
Max Planck is credited with the discovery of the "quantum," the discovery of which took place in December It was he who first wrote the equation above in his announcement of the discovery of the quantum.
Photoelectric effect (article) | Photons | Khan Academy
When discussing electromagnetic quanta of which light is only one example, x-rays and radio waves being two other examplesthe word photon is used. A photon the word is due to Albert Einstein is a quantum of electromagnetic energy.
The word quantum quanta is the plural is usually used in a more general sense, to describe various ideas of quantum theory or even, as I just did, to describe the entire theory itself. By the way, the discovery of the quantum had, and continues to have, many profound effects.
Enough so that all of science especially physics before is refered to as "classical" and the science since is called "modern. It is not a division, both Joule and second are in the numerator.
The discussion about frequency in part one applies here.Bohr Model of the Hydrogen Atom, Electron Transitions, Atomic Energy Levels, Lyman & Balmer Series
Before going on, I want to discuss one point. Frequency is a wave-based idea. What is it doing in a particle-based idea like the quantum? So much so that the term "wave packet" is often used in discussing these ideas.