photon

Examples of photon in the following topics:

• The Photoelectric Effect

  • If the photon energy is too low, the electron is unable to escape the material.
  • The energy of the emitted electrons does not depend on the intensity of the incoming light (the number of photons), only on the energy or frequency of the individual photons.
  • It is strictly an interaction between the incident photon and the outermost electron.
  • The number of electrons emitted also changes because the probability that each impacting photon results in an emitted electron is a function of the photon energy.
  • where h is the Planck constant (6.626 x 10-34 m2kg/s) and f is the frequency of the incident photon.

• Electromagnetic Spectrum

  • Electromagnetic waves are typically described by any of the following three physical properties: the frequency (f) (also sometimes represented by the Greek letter nu, ν), wavelength (λ), or photon energy (E).
  • Photon energy is directly proportional to the wave frequency, so gamma ray photons have the highest energy (around a billion electron volts), while radio wave photons have very low energy (around a femto-electron volt).
  • When electromagnetic radiation interacts with single atoms and molecules, its behavior also depends on the amount of energy per quantum (photon) it carries.
  • At very high energies, a single photon can create a shower of high-energy particles and antiparticles upon interaction with matter.
  • Calculate frequency or photon energy, identify the three physical properties of electromagnetic waves

• Photochemistry

  • The second law of photochemistry, the Stark-Einstein law, states that for each photon of light absorbed by a chemical system, only one molecule is activated for subsequent reaction.
  • This "photoequivalence law" was derived by Albert Einstein during his development of the quantum (photon) theory of light.
  • ", where an einstein is one mole of photons.

• Bonding in Metals: The Electron Sea Model

  • Light cannot penetrate their surface; the photons simply reflect off the metal surface.
  • However, there is an upper limit to the frequency of light at which the photons are reflected.

• The Electromagnetic Spectrum

  • The bottom equation describes this relationship, which provides the energy carried by a photon of a given wavelength of radiation.

• Mechanistic Background

  • In this section we shall focus chiefly on the nature and behavior of the electronic excited states formed when a photon is absorbed by a chromophoric functional group.
  • The electron reorganization that occurs when the ground electronic state is excited by absorption of a photon takes place much more rapidly than any movement of the atom nuclei that eventually follow.
  • The excited state may return to the ground state by emitting a photon (light blue line).
  • The distinction between singlet and triplet states is important because photon induced excitation always leads to a state of the same multiplicity, i.e. singlet to singlet or triplet to triplet.
  • Alternatively, an excited state may return to the ground state by emitting a photon (radiative decay).

• Aurora Borealis and the Aurora Australis

  • Auroras result from emissions of photons in the Earth's upper atmosphere (above 80 km, or 50 mi), from ionized nitrogen atoms regaining an electron, and from oxygen and nitrogen atoms returning from an excited state to ground state.
  • The excited particles' energy is lost by the emitting photon or colliding with another atom or molecule.
  • This energy serves to move the electrons in nitrogen and oxygen from their ground state up to an excited state, where they can then decay back to the ground state by emitting photons of visible light (see the concept on emission spectra for more information).

• Introduction

  • Photon energies associated with this part of the infrared (from 1 to 15 kcal/mole) are not large enough to excite electrons, but may induce vibrational excitation of covalently bonded atoms and groups.

• Coloring Agents

  • In a d–d transition, an electron in a d orbital on the metal is excited by a photon to another d orbital of higher energy.

• Balancing Nuclear Equations

  • Common light particles are often abbreviated in this shorthand, typically p for proton, n for neutron, d for deuteron, α representing an alpha particle or helium-4, β for beta particle or electron, γ for gamma photon, etc.