Photoelectric effect Light shining on a metal cause emission of electrons The energy of a wave is proportional to its intensity, the kinetic energy of emitted photoelectron would increase as the light intensity increases- the electromagnetic-wave picture the kinetic energy is independent of lights intensity - exper'iment In 1903. einstein light is composed of paticlelike entities(photons) hoton v=Φ+T
Increase in the lights frequency v increases the kinetic energy of the emitted electrons Increase in the lights intensity at fixed frequency L> increases the rate of the emission of electrons The photoelectric effect shows that light can exhibit particlelike behavior in addition to the wavelike ehavior
.The structure of matter In late 1800s, electrons(negative charge) proton(positive charge) 1836 times as heavy as electron neutron(uncharged, 1932) In 1904 Thomson the positive charge were spread through the atom In 1909 Rutherford a particle (helium i)passed through atom large deflections(大角度散射) 1911. Rutherfords planetary model the electrons revolved about the nucleus in various orbital