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Photoexcitation is the first step in a photochemical process where the reactant is elevated to a state of higher energy, an excited state.The first law of photochemistry, known as the Grotthuss–Draper law (for chemists Theodor Grotthuss and John W. Draper), states that light must be absorbed by a chemical substance in order for a photochemical reaction to take place.
An FM radio station transmitting at 100 MHz emits photons with an energy of about 4.1357 × 10 −7 eV. This minuscule amount of energy is approximately 8 × 10 −13 times the electron's mass (via mass–energy equivalence). Very-high-energy gamma rays have photon energies of 100 GeV to over 1 PeV (10 11 to 10 15 electronvolts) or 16 nJ to 160 ...
The Planck relation [1] [2] [3] (referred to as Planck's energy–frequency relation, [4] the Planck–Einstein relation, [5] Planck equation, [6] and Planck formula, [7] though the latter might also refer to Planck's law [8] [9]) is a fundamental equation in quantum mechanics which states that the energy E of a photon, known as photon energy, is proportional to its frequency ν: =.
Stimulated light emission—a theory first proposed by Einstein in 1916 that helps explain how photons can trigger atoms to emit other photons—laid the basis for the invention of the laser ...
Spontaneous emission is the process in which a quantum mechanical system (such as a molecule, an atom or a subatomic particle) transits from an excited energy state to a lower energy state (e.g., its ground state) and emits a quantized amount of energy in the form of a photon. Spontaneous emission is ultimately responsible for most of the light ...
A photon (from Ancient Greek φῶς, φωτός (phôs, phōtós) 'light') is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force.
By recording the attenuation of light for various wavelengths, an absorption spectrum can be obtained. In physics , absorption of electromagnetic radiation is how matter (typically electrons bound in atoms ) takes up a photon 's energy —and so transforms electromagnetic energy into internal energy of the absorber (for example, thermal energy ).
The light excites an electron in the pigment P680 at the core of photosystem II, which is transferred to the primary electron acceptor, pheophytin, leaving behind P680 +. The energy of P680 + is used in two steps to split a water molecule into 2H + + 1/2 O 2 + 2e-(photolysis or light-splitting).