With Forces and Light
4 Photoelectric effect
This is section 4 of 12 in the web-book.
The photoelectric effect resulted in the concept of a photon particle.
The photoelectric effect is the emission of electrons when electromagnetic radiation, such as light, hits a material. Electrons emitted in this manner are called photoelectrons.
The experimental results instead show that electrons are dislodged only when the light exceeds a certain frequency—regardless of the light's intensity or duration of exposure. Because a low-frequency beam at a high intensity could not build up the energy required to produce photoelectrons like it would have if light's energy was coming from a continuous wave, Albert Einstein proposed that a beam of light is not a wave propagating through space, but a collection of discrete wave packets, known as photons.
In 1905, Einstein proposed a theory of the photoelectric effect using a concept first put forward by Max Planck that light consists of tiny packets of energy known as photons or light quanta. Each packet carries hv energy that is proportional to the frequency v of the corresponding electromagnetic wave. The proportionality constant h has become known as the Planck constant.
The maximum kinetic energy Kmax of the electrons that were delivered this much energy before being removed from their atomic binding is
Kmax = hv – W
where W is the minimum energy required to remove an electron from the surface of the material.
Einstein's formula, however simple, explained all the phenomenology of the photoelectric effect, and had far-reaching consequences in the development of quantum mechanics.
Einstein described the phenomena but he did not justify a photon particle. He just used the work of Planck.
Planck proposed that the energy stored within a material object should be regarded as composed of an integer number of discrete, equal-sized parts. To explain the photoelectric effect, Einstein introduced the idea that light itself is made of discrete units of energy. In 1926, Gilbert N. Lewis popularized the term photon for these energy units. [Reference:
The energy requirement for the transfer of energy is defined by the atom.
The quantized behavior is in the atom, not in the light.
This scenario is like when a baby consistently accepts only a mouthful of milk from the bottle. The amount in a mouthful is defined by the baby, not by the milk from the bottle, or by the capacity of the bottle.
Light is a continuous stream of energy having a continuum of wavelengths, not a collection of discrete wave equal-sized packets.
Visible Light is a continuum of frequencies, essentially from violet to red. There are no discrete increments anywhere in this continuum of energy.
Our eyes see the combination of certain frequencies as white. Human eyes are not sensitive to only certain range of wavelengths.
Thermal radiation has the wavelength intensities set by th temperature of the source.
4.2 Nature of light
Note that section Light by Gardi also has important observations about the photoelectric effect and the energy in a wavelength of light.
4.3 Summary of section
Einstein misunderstood the experiment.
There is no photon.
Quantum mechanics just calls a wavelength of light a photon. The Standard Model of particle physics is based on particles, so even light and forces must be particles.
In the spectrum of light, wavelengths have no defined increment but span a continuum of values. The range is specified in whatever units are used, like Angstroms.
The units selected for a measurement cannot define a behavior.