Science / Chemistry / Photon: A discrete packet of energy associated with electromagnetic radiation. Each photon carries energy E proportional to the frequency nu of the radiation: E = hnu, where h is Planck's constant.


Science / Biology / Matter: Anything that has mass and occupies space. MORE


Science / Chemistry / Photoelectron: An electron ejected from an atom or molecule that has absorbed a photon. MORE

Excited State

Science / Chemistry / Excited State: An atom or molecule which has absorbed energy is said to be in an excited state. Excited states tend to have short lifetimes; they lose energy either through collisions or by emitting photons to 'rela MORE

Plancks Constant

Science / Chemistry / Plancks Constant: A proportionality constant that relates the energy carried by a photon to its frequency. Planck's constant has a value of 6.6262 × 10-34 J s. MORE

Photoelectric Effect

Science / Chemistry / Photoelectric Effect: Ejection of electrons from an atom or molecule that has absorbed a photon of sufficient energy. The photoelectric effect is the operating principle behind 'electric eyes'; it is experimental evidence MORE