Photoelectric Effect. Einstein's Photon Theory (光电效应、爱因斯坦光子理论 equipment Einstein assumed that the 光电管 A energy in a light beam travels K through space in concentrated is bundles, called photons. The energy e of a single photon is given by E=h Applying the photon r concept to the photoelectric E efifect. Einstein wrote K hV== nmy+A0…(10
equipment 2. Photoelectric Effect. Einstein’s Photon Theory (光电效应、爱因斯坦光子理论) R K1 K2 E G V les, called photons. Einstein assumed that the energy in a light beam travels through space in concentrated bund p i The energy E of a single photon is given by E = hv . Applying the photon concept to the photoelectric effect, Einstein wrote S I S i 光电管 K A (10) 2 1 0 2 h = mvmax + A
Equation above says that a photon carries an energy hy into the sur- electron face. Part of this energy Ao is used o hy in causing the electron to pass 金 through the metal surface. The 属A excess energy(hv-Ao) is given to the electron in the form of kinetic energv In 1916, Millikan, experiments verified einstein's ideas in eve ry detail Einstein succeed in explaining Fl the photoelectric effect. 图7-5密立根光电效应实验装置图
Equation above says that a photon carries an energy hv into the surface. Part of this energy A0 is used in causing the electron to pass through the metal surface. The excess energy (hv-A0 ) is given to the electron in the form of kinetic energy. In 1916, Milikan, experiments verified Einstein’s ideas in every detail. Einstein succeed in explaining the photoelectric effect. h - - 金 属 electron - - - A v
The dual nature of light, particle and wave 光的波粒二象性 particle wave (energy E ( frequency h (momentum) Po a (wavelength) These two natures are connected by h Eb=h…(1) E-E+(PC hv h P=E/C (2)
The dual nature of light, particle and wave 光的波粒二象性 particle wave （energy） （frequency） （momentum） （wavelength） E P h These two natures are connected by h. (1) E = h / (2) h C h P = E C = = 2 2 0 2 E = E + (P c)
3. The Compton effect(康普顿效应 Compelling confirmation of the concept of the photon as a concen trated bundle of energy was provided in 1923 by A.H. compton who earned a Noble prize for this work in 192/7 Mrn Compton allowed a beam of X-rays of sharply defined wavelengthito fall on a graphite block. He measured for various angles of scattering, the intensity of the scattered X-rays as a function of their wavelength
3. The Compton effect (康普顿效应) Compelling confirmation of the concept of the photon as a concentrated bundle of energy was provided in 1923 by A.H.Compton who earned a Noble prize for this work in 1927. Compton allowed a beam of X-rays of sharply defined wavelengthλto fall on a graphite block. He measured, for various angles of scattering, the intensity of the scattered X-rays as a function of their wavelength
1) Equipment 10.70A X射线分析仪 光石墨 X光栏 Compton allowed a beam of X-rays of sharpl defined wavelengthito fall on a graphite block. He measured, for various angles of scattering, the intensity of the scattered X-rays as a function of their wavelength
1) Equipment Compton allowed a beam of X-rays of sharply defined wavelengthλto fall on a graphite block. He measured, for various angles of scattering, the intensity of the scattered X-rays as a function of their wavelength.0 X光 光 栏 石墨 0.70Å X射线分析仪
D)Equipment q=00 10.70A 45 强度 光石墨 q=900 X光栏 2)Experimental results:9 OThe scattered X-rays have intensity 4 =135 peaks at two wavelengths: one of the them is the same as the incident wavelength, No, the other, 2, being larger by an amount△^ 0.70075x
1) Equipment 0 2) Experimental results : X光 光 栏 石墨 0.70Å X射线分析仪 2 3 4 1 =00 =450 =900 =1350 0.70 0.75 (Å) 强 度 The scattered X-rays have intensity peaks at two wavelengths: one of the them is the same as the incident wavelength, 0 , the other, , being larger by an amount △
q=0 钼辐射器,Ka线 @This So-called Compton 锂,128° M shift△ varies with the 硼,128° M angle at which the scattered X-rays are 碳,128° observed 水,128° ③ Compton shift△λfor 钠.128 M collisions with tightly 镁.约120° M bound electrons is 铝,约125 immeasurably small M T 图9-6康普顿和吴有训1924年发表的曲线 0.70075(A)
2 3 4 1 =00 =450 =900 =1350 0.70 0.75 (Å) 强 度 This so-called Compton shift △ varies with the angle at which the scattered X-rays are observed. Compton shift △ for collisions with tightly bound electrons is immeasurably small
3) Explain Compton Effect对康普顿效应的解释 Compton was able to explain his experimental results by postulation that the incoming X-ray beam was not a wave but an assembly of photons of energy e( hv) and that these photons expe rienced billiard -ball-like collisions with the free electrons in the scattering block hy hy 0 0 个A@X Before After
3) Explain Compton Effect 对康普顿效应的解释 Compton was able to explain his experimental results by postulation that the incoming X-ray beam was not a wave but an assembly of photons of energy E (= hv) and that these photons experienced billiard-ball-like collisions with the free electrons in the scattering block. h0 0 n ˆ m0 e X Before After h0 0 n ˆ e m V h
Analyze quantitatively Before After hv h 0 0 hvo po →Ⅹ Mom B efore After Electron Photon Electron Photon energy m c<+hv 0 hh momentum no= my Let us assume this is an elastic scattering collision
X Analyze quantitatively m0 e h0 0 n ˆ 2 m0 C m0 e n ˆ Before After Before After Electron Photon Electron Photon energy momentum 2 h 0 mC h 0 0 0 n ˆ C h n C h ˆ mV Let us assume this is an elastic scattering collision. + = + = + h0 0 n ˆ e m V h
Analyze quantitatively hv h hvo n mo X m a hv 0 Before After V hvo+m2C2=hy+mC2…(1) h pn0=m+n…(2) From(1)mC2=h(v0-)+mC2…(3) From the low of cosine hv hvhv (m7) CoSq…(4)
Analyze quantitatively Before After (1) 2 2 h 0 + m0 C = h + mC ˆ ˆ (2) 0 0 n C h n mV C h = + ( ) ( ) ( ) 2 cos (4) 2 0 2 2 0 C h C h C h C h m V = + − { n C h ˆ mV 0 0 n ˆ C h From（1） ( ) (3) 2 0 0 mC2 = h − + m C From the low of cosine X m0 e h0 0 n ˆ m0 e h0 n ˆ 0 n ˆ e m V h