photoelectric effects

(noun)

In photoelectric effects, electrons are emitted from matter (metals and non-metallic solids, liquids or gases) as a consequence of their absorption of energy from electromagnetic radiation.

Related Terms

Examples of photoelectric effects in the following topics:

  • The Photoelectric Effect

    • Electrons are emitted from matter that is absorbing energy from electromagnetic radiation, resulting in the photoelectric effect.
    • This is called the photoelectric effect, and the electrons emitted in this manner are called photoelectrons.
    • The photoelectric effect is also widely used to investigate electron energy levels in matter.
    • Heinrich Hertz discovered the photoelectric effect in 1887.
    • Explain how the photoelectric effect paradox was solved by Albert Einstein.

  • The Photoelectric Effect

    • The photoelectric effect is the propensity of high-energy electromagnetic radiation to eject electrons from a given material.
    • The photoelectric effect has been demonstrated using light with energies from a few electronvolts (eV) to over 1 MeV in high atomic number elements.
    • Study of the photoelectric effect led to an improved understanding of quantum mechanics as well as an appreciation of the wave-particle duality of light.
    • This, in essence, is the photoelectric effect.
    • Kinetic energy must be positive for ejection to take place, so we must have f > f0 for the photoelectric effect to occur.

  • Energy, Intensity, Frequency, and Amplitude

    • ., in medicine), as well as effects in nature.
    • The energy effects of a wave depend on time as well as amplitude.
    • In both cases, changing the area the waves cover has important effects.
    • However, this is not the case in the microscopic world, as shown in experiments on photoelectric effects (see our Atom on "Photoelectric Effect").
    • As Einstein postulated to explain photoelectric effects, a quantum of light (photon) carries a specific amount of energy proportional to the frequency of light.

  • Particle-Wave Duality

    • Photoelectric effect: Classical wave theory of light also fails to explain photoelectric effect.
    • In 1905, Albert Einstein explained the photoelectric effects by postulating the existence of photons, quanta of light energy with particulate qualities.

  • Planck's Quantum Theory

    • However, by the early 20th century, physicists discovered that the laws of classical mechanics are not applicable at the atomic scale, and experiments such as the photoelectric effect completely contradicted the laws of classical physics.
    • The wave model cannot account for something known as the photoelectric effect.
    • This effect is observed when light focused on certain metals emits electrons.
    • For each metal, there is a minimum threshold frequency of EM radiation at which the effect will occur.
    • However, in 1905, Albert Einstein reinterpreted Planck's quantum hypothesis and used it to explain the photoelectric effect, in which shining light on certain materials can eject electrons from the material.

  • de Broglie and the Wave Nature of Matter

    • He also demonstrated, in his study of photoelectric effects, that energy of a photon is directly proportional to its frequency, giving us this equation:
    • Therefore, the presence of any diffraction effects by matter demonstrated the wave-like nature of matter.
    • Just as the photoelectric effect demonstrated the particle nature of light, the Davisson–Germer experiment showed the wave-nature of matter, thus completing the theory of wave-particle duality.
    • Further, recent experiments confirm the relations for molecules and even macromolecules, normally considered too large to undergo quantum mechanical effects.

  • Energy, Mass, and Momentum of Photon

    • The modern photon concept was developed gradually by Albert Einstein to explain experimental observations of the photoelectric effect, which did not fit the classical wave model of light.
    • Energy of photon: From the studies of photoelectric effects, energy of a photon is directly proportional to its frequency with the Planck constant being the proportionality factor.

  • Radiation Detection

    • Gaseous ionization detectors use the ionizing effect of radiation upon gas-filled sensors.
    • PMTs absorb the light emitted by the scintillator and re-emit it in the form of electrons via the photoelectric effect.

  • X-Rays and the Compton Effect

    • In 1923, Compton published a paper in the Physical Review which explained the X-ray shift by attributing particle-like momentum to "photons," which Einstein had invoked in his Nobel prize winning explanation of the photoelectric effect.
    • Therefore, you can say that Compton effects (with electrons) occur with x-ray photons.
    • If the photon is of lower energy, but still has sufficient energy (in general a few eV to a few keV, corresponding to visible light through soft X-rays), it can eject an electron from its host atom entirely (a process known as the photoelectric effect), instead of undergoing Compton scattering.

  • Basic Assumptions of the Bohr Model

    • Soon after, Einstein resorted to this new concept of energy quantization and used the Planck constant again to explain the photoelectric effects, in which he assumed that electromagnetic radiation interact with matter as particles (later named "photons").