O Phyical chomitayI Chapter I Introduction of Quantum Meelanics 界 hataelectuic elect 20218/21 Chemistry Departme nt of Fudan University 16
Physical ChemistryI Chapter I Introduction of Quantum Mechanics 2021/8/21 Chemistry Department of Fudan University 16 金属 Photoelectric Effect
Phgyical ChemidkryI Chapter I Introduction of Quantum Mecltanics P. Lenard (1905 aBel uize) The frequency of the light Ec and not its intensity controls whether or not electrons are E￡E emitted The frequency which is just sufficient to remove the electron, is known as threshold Increasin equency c work function Frequency of incident radiation v 20218/21 Chemistry Departme nt of Fudan University
Physical ChemistryI Chapter I Introduction of Quantum Mechanics 2021/8/21 Chemistry Department of Fudan University 17 1. The frequency of the light and not its intensity controls whether or not electrons are emitted。The frequency which is just sufficient to remove the electron, is known as threshold frequency P.Lenard (1905 Nobel Prize）
O Phyical chomitayI Chapter I Introduction of Quantum Meelanics The number of electrons emitted is proportional to the intensity, and the electron emission occurs the instant the radiation strikes the metal surface if the frequency is above threshold. Classical Physics: The energy of the radiation should depend only on its intensity. Whether or not electrons are emitted should therefore depend on the energy of the radiation, and even low intensities, regardless of frequency, should be effective if long periods of time were allowed for their absorption. 20218/21 Chemistry Departme nt of Fudan University 18
Physical ChemistryI Chapter I Introduction of Quantum Mechanics 2021/8/21 Chemistry Department of Fudan University 18 Classical Physics：The energy of the radiation should depend only on its intensity. Whether or not electrons are emitted should therefore depend on the energy of the radiation, and even low intensities, regardless of frequency, should be effective if long periods of time were allowed for their absorption. 2. The number of electrons emitted is proportional to the intensity, and the electron emission occurs the instant the radiation strikes the metal surface if the frequency is above threshold
O Phyical chomitayI Chapter I Introduction of Quantum Meelanics Einstein’ s Theory 1. Light itself is a beam of particles each of which has energy equal tohv and momentum to p=h/n 2. Photons obey the laws of conservation of energy and momentum when the photons interact with the materia 3. The intensity of light is proportional to the number of photons per unit volume in the beam 20218/21 Chemistry Departme nt of Fudan University
Physical ChemistryI Chapter I Introduction of Quantum Mechanics 2021/8/21 Chemistry Department of Fudan University 19 2. Photons obey the laws of conservation of energy and momentum when the photons interact with the material. Einstein’s Theory 1. Light itself is a beam of particles each of which has energy equal to h and momentum to p = h / . 3. The intensity of light is proportional to the number of photons per unit volume in the beam
O Phyical chomitayI Chapter I Introduction of Quantum Meelanics The explain of photoelectric effect kinetic energy K=e(radiation )-work function w gnetc energy of ejected electron Energy needed Aamv to remove electron from metal 力v 20218/21 Chemistry Departme nt of Fudan University
Physical ChemistryI Chapter I Introduction of Quantum Mechanics 2021/8/21 Chemistry Department of Fudan University 20 The Explain of Photoelectric effect kinetic energy K = E (radiation)- work function W