1. History of Quantum Mechanics The concept of the wave nature of atomic particles. This is the foundation of the mathematical discipline. (1) From wave mechanics we can understand and predict the properties of molecules as individual entities (the so-called microscopic state); (2) The properties of molecules(the macroscopic state) can be obtained by applying statistical techniques to these microscopic results
Matter Waves 1. History of Quantum Mechanics The concept of the wave nature of atomic particles. This is the foundation of the mathematical discipline. (1) From wave mechanics we can understand and predict the properties of molecules as individual entities (the so-called microscopic state) ;(2) The properties of molecules (the macroscopic state) can be obtained by applying statistical techniques to these microscopic results
The birth of wave mechanics:(1)1924, de Broglie postulated that material particles would show wave-like characteristics; (2)1926, Schrodinger introduced an equation to define these characteristics. (3)1900, First proposed the conception of‘ quanta’ Quantum development: (1) The ' old quantum mechanics: Associate with the Bohr model of the atom;(2) The ' quantum mechanics: Associate mainly with the work of Heisenberg.(What is the aim of quantum mechanics proposed?)
The birth of wave mechanics: (1) 1924, de Broglie postulated that material particles would show wave-like characteristics;(2)1926, Schrödinger introduced an equation to define these characteristics. (3)1900, First proposed the conception of ‘quanta’. Quantum development: (1) The ‘old’ quantum mechanics: Associate with the Bohr model of the atom; (2) The ‘new’ quantum mechanics: Associate mainly with the work of Heisenberg. (What is the aim of quantum mechanics proposed?)
de broglie postulation: 1927, Verified by Davisson and germer. They showed that mono-energetic electrons scattered from crystalline nickel foil gave a diffraction pattern analogous to that showed by X-rays Similar experiments were carried out independently by G. P. Thomson, and later Stern showed that beams of heavier particles (H, He, etc.) showed diffraction patterns when reflected from the surfaces of crystals de broglie's expression for the wavelength of these matter waves is of high accuracy
de Broglie postulation:1927,Verified by Davisson and Germer. They showed that mono-energetic electrons scattered from crystalline nickel foil gave a diffraction pattern analogous to that showed by X-Rays. Similar experiments were carried out independently by G. P. Thomson, and later Stern showed that beams of heavier particles (H, He, etc.) showed diffraction patterns when reflected from the surfaces of crystals. de Broglie’s expression for the wavelength of these matter waves is of high accuracy
2. The wave-particle duality of light (1) Particle Character: The fact that light travels in straight lines, is reflected and refracted and has the ability to impart momentum to anything it strikes -Particulate model (2)Wave Character: The phenomena of diffraction and interference-Wave model When quantum theory was proposed the wave model was dominant The electromagnetic spectrum: Fig. 1 (The visible light is all band of electromagnetic
2. The wave-particle duality of light (1) Particle Character:The fact that light travels in straight lines, is reflected and refracted and has the ability to impart momentum to anything it strikes. -- Particulate model. (2) Wave Character: The phenomena of diffraction and interference.--Wave model. When quantum theory was proposed the wave model was dominant. The electromagnetic spectrum:Fig.1 (The visible light is all band of electromagnetic)
log(/m 210-1-2-3-4-5-6-7-8-9-10 Radio Microwave Ultro X-Ray Ⅴ iolet Ihfrared Visible (The speed of light in vacuum is dependence with frequency and wavelength?) The photoelectric effect: Light is able to cause electrons to be ejected from the surface of metals
(The speed of light in vacuum is dependence with frequency and wavelength?) The photoelectric effect:Light is able to cause electrons to be ejected from the surface of metals
1902: Lenard's study: Investigation of the relationship between the frequency and the intensity of light on the one hand and the number and kinetic energy of ejected electrons on the other. Fig. 2 shows the relationship between the frequency and the kinetic energy per electron 1905: Einstein extended Planks Hypothesis that atomic oscillators could not only take up or give out energy in discrete quanta, by regarding the radiation itself as consisting of indivisible quanta or photons
1902:Lenard’s study: Investigation of the relationship between the frequency and the intensity of light on the one hand and the number and kinetic energy of ejected electrons on the other. Fig.2 shows the relationship between the frequency and the kinetic energy per electron. 1905 :Einstein extended Plank’s Hypothesis that atomic oscillators could not only take up or give out energy in discrete quanta, by regarding the radiation itself as consisting of indivisible quanta or photons
an Frequency(n Fig. 2 The relationship between the kinetic energy of the electrons emitted from a metal surface and frequency of the light incident upon it
Energy Frequency() Kinetic Energy per electron Fig.2 The relationship between the kinetic energy of the electrons emitted from a metal surface and frequency of the light incident upon it
Plank-Einstein relationship e=hv (1) The proportionality constant h relating the energy of a photon to its frequency turned out to be the one introduced by Plank in his theory. so-called as Plank constant. The particulate interpretation of the photoelectric effect is straightforward. Each photon absorbed by a metal can lead to emission of one electron providing that the energy of the photon, when transferred to the electron, is sufficient to enable the electron to escape
Plank-Einstein relationship E = h (1) The proportionality constant h relating the energy of a photon to its frequency turned out to be the one introduced by Plank in his theory. So-called as Plank constant. The particulate interpretation of the photoelectric effect is straightforward. Each photon absorbed by a metal can lead to emission of one electron providing that the energy of the photon, when transferred to the electron, is sufficient to enable the electron to escape
from the surface of the metal. Increasing the intensity of the light increases the number of electrons but not their energy and so will lead to an increase in the number of electrons escaping but not to an increase in their energy The kinetic energy of the ejected electron is mv2/2. where m is the mass of the electron and v is the velocity, we may write an equation for the energy balance in the experiment: hv=A+mv2/2(2)where A is an energy characteristic of the metal surface
from the surface of the metal. Increasing the intensity of the light increases the number of electrons but not their energy and so will lead to an increase in the number of electrons escaping but not to an increase in their energy. The kinetic energy of the ejected electron is mv2 /2, where m is the mass of the electron and v is the velocity, we may write an equation for the energy balance in the experiment: h = A + mv2 /2 (2) where A is an energy characteristic of the metal surface
This interpretation of the photoelectric effect restored the balance between the wave and particle models for light, and the position adopted today is that light has a wave. particle duality An important aspect of the treatment of the Compton effect is the conservation of the momentum of the colliding particles. But how can a photon, which has no mass, have momentun? Similarly, in writing the energy of the photon in equation(2)as hywe avoided any discussion of the form of this
This interpretation of the photoelectric effect restored the balance between the wave and particle models for light, and the position adopted today is that light has a waveparticle duality. An important aspect of the treatment of the Compton effect is the conservation of the momentum of the colliding particles. But how can a photon, which has no mass, have momentun? Similarly, in writing the energy of the photon in equation (2) as h we avoided any discussion of the form of this
