1. MODERN PHYSICS Physics from 1900 to the present

2. BLACKBODY RADIATION A blackbody is an ideal object that absorbs all the radiation incident on it, and then reradiates energy. All objects emit electromagnetic radiation, some freqs. can be seen, others can not. Classical theory did not match experimental data. Max Planck (1858-1947) theory of quantized energy

3. Brightness vs. Wavelength InfraredUltraviolet

4. Wien’s Displacement Law The peak of the distribution curve can be found by the following relationship: Our Sun5800 K Betalgeuse2900 K Humans 300 K Campfire1500 K

6. E = nhf Planck’s equation describes the energy associated with the frequency of an electromagnetic wave. Energy only found in discrete units or bundles called “photons.” h = 6.63 x 10 -34 Js is called Planck’s constant. And n is an integer

7. MAX PLANCK

8. THE ELECTRON VOLT An electron volt is a unit of energy equal to the kinetic energy that one electron obtains when accelerated through a potential difference of 1 volt. 1 eV = 1.6 x 10 -19 J Planck’s constant in terms of electron voltsh = 4.14 x 10 -15 eV s

9. PHOTOELECTRIC EFFECT The emission of electrons from the surface of certain metals due to incident radiation (Discovered by Hertz). Emitted electrons are called “photoelectrons.” Experimented on by Ernest Rutherford. Theory explained by Einstein in 1905; he then won the Nobel Prize in Physics for the predictions.

11. Photoelectric Effect Observations Electrons were emitted immediately. Increased light intensity only increased number of photoelectrons emitted not their Kinetic energy. Increased frequencies only increased photoelectron’s kinetic energy not the number of them.

13. PHOTOELECTRIC EFFECT Analysis of Data Electrons are emitted only when the frequency of the light is above a threshold level. The maximum kinetic energy of the emitted electrons depends only on the frequency of the incident light. The number of electrons depends only on the intensity of the light.

14. PHOTOELECTRIC EFFECT Conclusions and connections: –Light behaves like a particle –Einstein prediction that max. energy should be hf + energy lost pulling electron loose –Connection to Planck’s quantum theory of quantum bundles of energy –Slope of graph of Energy vs. frequency is h, Planck’s Constant

15. PHOTOELECTRIC EQUATION The frequency of the incident light Work function of the metal

16. WORK FUNCTIONS OF COMMON METALS Sodium (Na)2.46 eV Aluminum (Al)4.08 eV Copper (Cu)4.70 eV Silver (Ag)4.73 eV Platinum (Pt)6.35 eV

17. Slope = h (Planck’s constant)

18. STOPPING VOLTAGE Reverse the polarity of the plates, and there is a voltage that will cause the photoelectrons to not be emitted. This voltage is called the stopping voltage. KE max = eV s + -

19. AL EINSTEIN

20. COMPTON EFFECT Arthur H. Compton (1922) showed that photons of x-rays collide with electrons and carom like in a particle collision. After collision the x-ray frequency is decreased, i.e. wavelength increased. Concluded that electromagnetic waves have momentum.

22. MATTER WAVES Louis de Broglie (1924) theorized that matter in motion has wave-like properties. Particle in motion must exhibit a wavelength. Waves behave like particles-particles behave like waves…this is called wave-particle duality

23. LOUIS De BROGLIE

24. Light Microscope Images vs. Electron Microscope Images

27. HEISENBERG UNCERTAINTY PRINCIPLE One measuring the location and/or the momentum (motion) of a particle can never know with complete certainty both. The measurer by merely measuring affects the location and/or the momentum of the particle.

28. Black Box Definition: A device, system, object, idea, etc. that can only be viewed from it’s inputs and outputs.

29. MODELS OF THE ATOM Greek Democritus (460 BC) suggested that matter was composed of individual particles called atoms. Joseph J. Thomson (1856-1940) view of atom was similar to “plum-pudding.” Positive charge formed a “paste” in which electrons were suspended within.

30. PLUM PUDDING MODEL

31. J.J. THOMPSON

32. GOLD-FOIL EXPERIMENT Ernest Rutherford (1911) bombarded gold-foil with alpha particles. Positively charged nucleus containing most of atom’s mass. Electrons moving around nucleus like the planets around the Sun. Atom is mostly empty space.

33. ERNEST RUTHERFORD

35. PLANETARY MODEL

36. BOHR MODEL Based upon spectroscopy of gases. Filament of light bulb emits continuous range of wavelengths. Individual atoms emit only certain specific wavelengths. Emission spectrum of element like a fingerprint for that atom.

38. BOHR MODEL Bohr Postulates: –Electrons orbit the nucleus at certain discrete radii. –They do not lose energy if they remain in the same orbit. –They emit a photon of energy if they drop to a lower orbit. –They absorb the same energy if raised back to original orbit.

39. n=1 n=2 n=3 n=4 n=5 0.00 eV -13.60 eV -3.40 eV BOHR MODEL HYDROGEN -1.51 eV -0.85 eV -0.54 eV

40. Bohr Model

41. NYS Reference Table

42. Schrodinger’s Equation

43. STANDARD MODEL Most recent model of the atom developed over decades. Classification of all sub-atomic particles which are naturally occurring and man-made. Matter is composed of these particles which interact by exchanging force particles.

44. STANDARD MODEL 4 known forces: –Gravitational- –Electromagnetic* –Weak nuclear* –Strong nuclear *In the mid-1960’s the electromagnetic force and the weak force were unified into one force called the electroweak force.

45. STANDARD MODEL

46. NYS Reference Table

48. FERMILAB

49. Hottest Topic- String Theory

50. String Theory Answer to Unification?

51. Brian Greene

52. CERN: French for European Laboratory for Particle Physics;

53. SUPER KAMIOKANDE neutrino trap

54. NUCLEAR PHYSICS The nucleus consists of 2 main particles, protons and neutrons The atomic number (Z) equals the number of protons in the nucleus The neutron number (N) equals the number of neutrons The mass number (A) equals Z+N, or the number of nucleons

55. NUCLEAR SYMBOLS Atomic # Mass # Chemical Symbol

56. NUCLEAR REACTIONS Beta Decay

57. NUCLER REACTIONS Alpha Decay

58. NUCLEAR REACTIONS Gamma Decay

59. ENERGY AND MASS Unified mass number (u) is based upon the carbon-12 nucleus 1 u = 1.67 x 10 -27 kg The rest energy of u can be found by E=mc 2 1 u has the energy of 931 MeV

60. FISSION REACTION

68. FUSION REACTION

69. Models of the Atom Quiz Question 1 –Describe what a blackbody is, and explain why one star may be yellow in color while another may be red.

70. Models of the Atom Quiz Question 2 –In the equation E=hf, what is the name and value of h.

71. Models of the Atom Quiz Question 3 –What is a photon?

72. Models of the Atom Quiz Question 4 –Explain in exactly one sentence Wave/particle Duality.

73. Models of the Atom Quiz Question 5 –Draw the Rutherford planetary model of the atom.

74. Models of the Atom Quiz Question 6 –Using the Bohr model of the hydrogen atom, determine the energy emitted from a n=6 to n=2 transition.

75. Models of the Atom Quiz Question 7 –Calculate the wavelength and frequency of the photon emitted from question 6.

76. Models of the Atom Quiz Question 8 –What type of photon is the photon from question 7?

77. Models of the Atom Quiz Question 9 –A mercury atom is ionized from the g level, determine the frequency of the absorbed photon.

78. Models of the Atom Quiz Question 10 –Determine the charge of a ddt quark combination.

79. Models of the Atom Quiz Bonus question –What are the four known forces, and why should you have answered only three?

80. Question 1 Answer A blackbody is a theoretical object that radiates the maximum amount of energy at a given temperature, and absorbs all the energy incident upon it.

81. Question 2 Answer h is Planck’s Constant. It’s value is 6.63 x 10 -34 Js

82. Question 3 Answer A photon is an individual packet of electromagnetic energy that makes up electromagnetic radiation.

83. Question 4 Answer Wave/particle Duality is the characteristic of matter to behave like waves and waves to behave like matter in certain experiments.

84. Question 5 Answer The Rutherford-planetary Model

85. Question 6 Answer n=6 is at -0.38eV and n=2 is at -3.40eV -0.38eV-(-3.40eV)=3.02eV 3.02eV=4.83 x 10 -19 J

86. Question 7 Answer

87. Question 8 Answer The photon is violet in color.

88. Question 9 Answer 5.98x10 14 Hz

89. Question 10 Answer 0

90. Bonus Answer Gravitational Electromagnetic Strong nuclear Weak nuclear The electromagnetic force and the weak nuclear force were unified in the 1960’s