The experimental basis of quantum theory
|
|
- Russell Montgomery
- 5 years ago
- Views:
Transcription
1 The experimental basis of quantum theory
2 Preliminary remarks New theories do not appear from nowhere, they are usually based on (unexplained) experimental results. People have to be ready for it, e.g. be able to interpret what they see as a new phenomenon and not an experimental flow in their setup. This also means being aware of new developments in physics Louis Pasteur (France, ) In the fields of observation, chance only favors the prepared mind (1854)
3 Part I: Blackbody Radiation Max Planck Nobel Prize in Physics 1918
4 Thermal Radiation Known since centuries that when a material is heated, it radiates heat and its color depends on its temperature Example: heating elements of a stove: Dark red: 550ºC Bright red: 700ºC Then: orange, yellow and finally white (really hot!) The emission spectrum depends on the material Theoretical description: simplifications necessary à Blackbody Thermal images taken before and after the zombie apocalypse
5 A material is constantly exchanging heat with its surrounding (to remain at a constant temperature): It absorbs and emits radiations Problem: it can reflect incoming radiations, which makes a theoretical description more difficult (depends on the environment) A blackbody is a perfect absorber: Incoming radiations is totally absorbed and none is reflected Blackbody Blackbody = a cavity, such as a metal box with a small hole drilled into it. Incoming radiations entering the hole keep bouncing around inside the box with a negligible chance of escaping again through the hole à Absorbed. The hole is the perfect absorber, e.g. the blackbody Radiation emission does not depend on the material the box is made of à Universal in nature
6 Blackbody radiation
7 Wien s displacement law The intensity (λ, T) is the total power radiated per unit area per unit wavelength at a given temperature Wien s displacement law: The maximum of the distribution shifts to smaller wavelengths as the temperature is increased. Originally an empirical formula Wilhem Wien Nobel Prize (Physics) 1911 Visible light: nm Ultra-violet: <400 nm Infrared: >700 nm
8 Exercise - blackbody Dominant color of a blackbody at: T=4000ºC l = 678 nm RED T=5000ºC l = 549 nm GREEN T=6000ºC l = 461 nm BLUE
9 Stefan-Boltzmann Law The total power radiated per unit area increases with the temperature: This is known as the Stefan-Boltzmann law, with the constant σ experimentally measured to be W / (m 2 K 4 ). The emissivity є (є = 1 for an idealized blackbody) is simply the ratio of the emissive power of an object to that of an ideal blackbody and is always less than 1.
10 Understanding the blackbody spectrum Attempts to fit the low and high wavelength part of the spectrum Using classical theory of electromagnetism and thermodynamics, Lord Rayleigh comes up with: Rayleigh-Jeans formula Major flaw at short wavelength ( Ultraviolet catastrophe ) Describing the blackbody emission spectra: one of the outstanding problems at the beginning of the 20 th century
11 Two catastrophes? Classical physics: Emission spectrum: a superposition of electromagnetic waves of different frequencies Frequencies allowed: standing waves inside the cavity Equipartition of the energy: Every standing wave carries kt of energy Flaw: when l à 0, the number of standing waves à, leading to E à [Ultraviolet Catastrophe] Failure of classical theories: The work of Rayleigh-Jeans was considered as state-of-the-art, using well tested theories, which were in very good agreement with experimental results in many other circumstances. Need for a new theory
12 Max Planck and the blackbody problem Max Planck Expert in thermodynamics and statistical mechanics Around 1900: Proposes first an empirical formula (based on real physics) to reproduce both the high and low wavelength parts of the emission spectrum à Remarkable agreement with experimental results Then, works on a theoretical basis of the formula
13 Planck s radiation law Planck assumed that the radiation in the cavity was emitted (and absorbed) by some sort of oscillators contained in the walls. He used Boltzman s statistical methods to arrive at the following formula: Planck s radiation law Planck made two modifications to the classical theory: The oscillators (of electromagnetic origin) can only have certain discrete energies determined by E n = nhn, where n is an integer, n is the frequency, and h is called Planck s constant. h = J s. The oscillators can absorb or emit energy in discrete multiples of the fundamental quantum of energy given by DE = hn
14 Quantization! Blackbody emission spectrum explained by introducing quantization of energy transfers, resolves the ultraviolet catastrophe Low wavelength ßà High frequency (n = c/l) At small l, the energy E=hn needed to fill up the oscillator states increases. Their probability to be occupied decreases rapidly, e.g. faster than the rate found in the Rayleigh-Jeans formula: no ultraviolet catastrophe. Very disputed Planck himself looked for a few years in ways to get hà0 without success.
15 Quantum theory needed! Planck s radiation law Power radiated at a given frequency for a given blackbody temperature Power radiated at a given wavelength for a given blackbody temperature: Planck s radiation law
16 PHGN324: Why is blackbody radiation relevant to astronomy & astrophysics? A blackbody is a perfect absorber: incoming radiations is totally absorbed and none is reflected. The Sun (and any other stars) can be approximated to a Black Body: Almost a perfect absorber (Near) thermal equilibrium At the top of the atmosphere
17 PHGN324: Star color / temperature / Luminosity CLASSIFICATION: TEMPERATURE (K): Luminosity: where Hertzsprung-Russell (H-R) diagram Luminosity vs temperature L = 4π R 2 σt 4 R the radius of the star T the temperature of the star s the Stefan-Boltzmann constant (s=5.67x10-8 W.m -2.K -4 )
18 PHGN324: The Cosmic Microwave Background (CMB) Cosmic Microwave Background (CMB) CMB anisotropy 16 µk, DT/T=5 x 10-6 The CMB suggests that, at some point, the Universe was extremely dense and hot, and filled with radiation in THERMAL EQUILIBRIUM = Blackbody. After the time of last scattering (T~3000K - when the universe becomes transparent to radiation), the radiation cools off (redshift) due to the expansion of the Universe (now: T~2.728K)
19 Exercise Black hole temperature! A black hole may well be the perfect absorber. Famous astrophysicist Stephen Hawking suggests that a black hole can radiate energy with a thermal spectrum due to quantum effects (Hawking radiation). Lets consider a black hole as a sphere with a radius of 30km radiating 8.8x10-31 W of such thermal radiation. What would be the temperature of this black hole (in K)? [Hint: remember that the power is radiated from the surface of the black hole].
20 Part II: X-ray, Electrons and Line Spectra
21 Cathode rays Known since 1800 s Produced by a large difference of potential in an evacuated tube.
22 A brief history of cathode rays (and vacuum) 1833: Michael Faraday ( ) Study of electrical discharge of gas Notices that: rarefaction of the air wonderfully favors the glow phenomena à Poor vacuum 1858: Julius Plücker ( ) Seems to observe a deflection of the rays, when approaching a magnet Bright green glow around the cathode? à Still poor vacuum 1869 Johann Hittorf ( ) Reports that the glowing originates from the cathode Observes sharp shadows, the rays are traveling in straight lines à Better vacuum 1879 William Crookes reaches 40x10-3 mm Hg
23 Approaching the 20 th century The debate heats up: 1892: Heinrich Hertz claims experimental evidences that cathode rays cannot be particles 1895: Jean-Baptiste Perrin shows that cathode rays are negatively charged particles Cathode rays: Waves or Particles? In 1895, no one knows what cathode rays really are, but some of their properties were measured. So, the studies go on
24 The discovery of X-rays (I) Wilhem Röntgen ( ) on the evening of Nov 8, 1895 While working on cathode rays, notices that more penetrating rays are emitted from the interaction of the cathode rays with the tube, fluorescence on a nearby screen Measures the transmission of the rays through various materials. They appear to be transparent to the rays. Finally put his hand in front of rays and sees his bones on the screen!
25 The discovery of X-rays (II) Röntgen does not say anything to anybody. Astonished by his discovery, needs to check, double-check, triplecheck for about 7 weeks! Properties of the X-rays: More penetrating than cathode rays Not deviated by electric/magnetic fields Immediate medical applications! Finally, on Dec 28, 1895, he submits a preliminary paper: On a new kind of rays which is distributed in January 1896 By the end of 1896, more than a thousand papers were written on the subject of X- rays. 1902: Röntgen receives the first Nobel Prize in Physics
26 Nature of the cathode rays: the discovery of the electron J.J.Thomson (Nobel Prize 1906) Manages to show conclusively that cathode rays are deflected by electric and magnetic fields; do not depend on the material the cathode or the anode is made of. Have a negative charge, cathode rays are particles Measures e/m ratio, close (about 35% off) to the present value of 1.76x10 11 C/kg à Better vacuum available after progress by Crookes
27 An electron moving through the electric field is accelerated by a force: F + = ma + = qe = ee Electron angle of deflection: Measurement of the e/m ratio tan θ = v + v 4 = a +t v / = ee m The magnetic field deflects the electron against the electric field force. F = qe + qv B The magnetic field is adjusted until the net force is zero. l v / 7 E = v B v = E B = v / Charge-to-mass ratio: e m = v / 7 tan θ El = E tan θ B 7 l
28 Determination of the electron charge Robert Millikan oil drop experiment ( ) Used an electric field and gravity to suspend a charged oil drop. 8 F = 0 e E = m g Mass is determined from Stokes s relationship of the terminal velocity to the radius, and the density. m = 4 3 πra ρ Magnitude of the charge on the oil drop. e = mgd V Thousands of experiments showed that there is a basic quantized electron charge. e = IJK C
29 The electron J.J. Thomson: M N = JJ C/kg R. Millikan: e = 1.6x10-19 C; Electron charge: -e à m e = 9.1x10-31 kg The e/m e ratio was much larger (x1000) than expected (based on results with the Hydrogen atom ). This is due to the fact that: à m(h + )=m(proton)~1836 x m e Conclusions: both the mass and the charge of the electron are quantified
30 Line spectra d sin θ = nλ With d: distance between slits. It is observed that chemical elements produce unique colors when burned (with a flame) or excited (with an electrical discharge) Diffraction creates a line spectrum pattern of light bands and dark areas on the screen. The line spectrum serves as a fingerprint of the gas that allows for unique identification of chemical elements and material composition.
31 Absorption vs Emission spectrum
32 The line spectra of stars (I) Absorption spectrum of stars: Inner, dense layers of the star produce a continuous (blackbody) spectrum Cooler surface layers absorb light at specific wavelengths / frequencies
33 The line spectra of stars (II): assessing how old is a star Metal-poor star (very old star) Metal-rich star (relatively young star) The Sun is a metal-rich star
34 Balmer series In 1885, Johann Balmer (a swiss schoolteacher) finds an empirical formula for wavelength of the visible hydrogen line spectra in nm: λ = k7 k 7 4 nm (where k = 3,4,5 ) à Underlying order/quantification not understood
35 As more spectral lines are discovered, a more general empirical equation appears: the Rydberg equation: 1 λ = R Y 1 n 7 1 k 7 R Y = [ m IJ Rydberg equation Rydberg constant (for Hydrogen)
36 Exercise Find the Balmer formula from the Rydberg equation Determine a formula for the Lyman series (n=1) and the Pashen series (n=3)
37 Conclusions so far. Early experiments point to a quantization of certain quantities Quantization appears in empirical formula as a way to describe Nature Still no theory can explain the observed behaviors Does an accurate description of Nature indeed require quantization?
38 Part III: The Photoelectric Effect
39 The photoelectric effect Photoelectric effect: electrons are emitted from any surface (especially clean metal surface) when light of a sufficiently high-frequency (e.g. short wavelength) shines on that surface
40 Typical experimental setup Incident light triggers the emission of (photo)electrons from the cathode Some of them travel toward the collector (anode) with an initial kinetic energy The applied voltage V either accelerates (if positive) or decelerates (if negative) the incoming electrons. The intensity I of the current measured by the ammeter as a function of the applied voltage V is a measurement of the photoelectron properties, and therefore a measurement of the properties of the photoelectric effect.
41 Measurements Work done mostly by Philipp Lenard (Nobel prize in Physics 1905) Known properties since about 1902 When applying a negative (retarding) potential, it is possible to stop all the incoming electrons: K max (e - ) = ev 0
42 Measurements
43 Measurement #1 The amount of photoelectrons is proportional to the incident light intensity (same frequency) The retarding potential does not depend on the incoming light intensity: K max is not a function of I Classical: K max should be a function of I
44 Measurement #2 The retarding potential depends on the frequency: Higher frequencies generates higher energy electrons Classical theory: cannot explain this either!
45 Work function Work function f: minimum extra energy that allows electrons to escape the material. ev (electron-volt: energy gained by an electron in an accelerating potential of 1V) New unit of energy: 1 ev = 1.6 x J
46 Measurement #3 The smaller the work function f of the emitter material, the smaller is the threshold frequency f of the light that can eject photoelectrons No electrons are produced below this frequency whatever the intensity of the incident light. Classical theory: cannot explain this either!
47 Measurement #4 Photoelectric current is proportional to the light intensity the number of photoelectrons produced is proportional to the intensity of the incoming light Classical theory: Yes!
48 Takes Planck s ideas a step further Einstein s theory (1905) Suggests that the electromagnetic radiation field itself is quantized. Quanta of light carry a energy E=hn (photons) h: Planck s constant ; n: frequency of light Travels at the speed of light: ln = c Photoelectric effect: when a photon collides with an electron, it gives away all its energy (which is transferred to the electron as kinetic energy) Collision: Photon = Particle! Nobel Prize 1921 ( for the theory of the photoelectric effect and other significant contributions
49 The miracle year 1905 Theory of the Photoelectric Effect (p.132) Explanation of the Brownian Motion (p. 549) Special Theory of Relativity (p.891) Published in the same volume of Annalen der Physik, volume 17 (1905)
50 Einstein s theory Conservation of the energy: hn = f + K e - Energy of the incoming photon Kinetic Energy of the electron Kinetic Energy of the electron (non-relativistic): Work function (e.g. energy necessary for the electron to escape the material) Experimentally: K e - max = (1/2)m e -v max 2 = ev 0 Retarding Potential
51 Einstein s theory From hυ = φ + K c M`ab hυ φ = ev / With One gets φ = hυ / h υ υ / = ev / Frequency: f or n
52 Exercise What is the threshold frequency n 0 for the photoelectric effect on lithium (f=2.93ev)? What is the stopping potential if the wavelength of the incident light is 400nm?
53 Part IV: Compton scattering
54 The Compton effect Another compelling proof of the particle nature of light: The scattered photon is measured to have a longer wavelength (lower frequency) than the original photon à Cannot be explained by classical e.m.
55 Conservation of Energy: Conservation of Momentum: Combining the two conservation laws: With υ = d e and λ = λg λ, one finds: Analysis (see derivation) E : hυ + m M c 7 = hυ g + m M c p M c 7 p 4 : hυ c = hυg c cos θ + p M cos φ p + : 0 = hυg c sin θ p M sin φ hυg c sin θ = p M sin φ p (p + ) 7 p 7 M = ( hυ c )7 +( hυg c )7 2( hυ c )(hυg ) cos θ c E 7 h υ υ g + m M c 7 7 = m M c ( op d )7 +( opq d )7 2( op m M c 7 υ υ g = hυυ g 1 cos θ λ = λ g λ = h m M c d )(opq d ) cos θ 1 cos θ
56 Analysis (f = υ, f g = υ g )
57 Experimental results
58 Exercise What is the energy of the photon resulting from the scattering of a 662-keV g-ray at 30º?
59 Pair production
60 Annihilation Matter Antimatter collision à release of pure energy
CHAPTER 3 The Experimental Basis of Quantum Theory
CHAPTER 3 The Experimental Basis of Quantum Theory 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 Discovery of the X Ray and the Electron Determination of Electron Charge Line Spectra Quantization As far as I can
More informationCHAPTER 3 Prelude to Quantum Theory. Observation of X Rays. Thomson s Cathode-Ray Experiment. Röntgen s X-Ray Tube
CHAPTER Prelude to Quantum Theory.1 Discovery of the X Ray and the Electron. Determination of Electron Charge. Line Spectra.4 Quantization.5 Blackbody Radiation.6 Photoelectric Effect.7 X-Ray Production.8
More informationCHAPTER 3 The Experimental Basis of Quantum
CHAPTER 3 The Experimental Basis of Quantum 3.1 Discovery of the X Ray and the Electron 3.2 Determination of Electron Charge 3.3 Line Spectra 3.4 Quantization 3.5 Blackbody Radiation 3.6 Photoelectric
More informationPhysics Lecture 6
Physics 3313 - Lecture 6 Monday February 8, 2010 Dr. Andrew Brandt 1. HW1 Due today HW2 weds 2/10 2. Electron+X-rays 3. Black body radiation 4. Compton Effect 5. Pair Production 2/8/10 3313 Andrew Brandt
More informationStellar Astrophysics: The Interaction of Light and Matter
Stellar Astrophysics: The Interaction of Light and Matter The Photoelectric Effect Methods of electron emission Thermionic emission: Application of heat allows electrons to gain enough energy to escape
More informationFI 3103 Quantum Physics
FI 3103 Quantum Physics Alexander A. Iskandar Physics of Magnetism and Photonics Research Group Institut Teknologi Bandung General Information Lecture schedule 17 18 9136 51 5 91 Tutorial Teaching Assistant
More informationExperimental Basis for QM Ch3
Experimental Basis for QM Ch3 This chapter describes the early evidence for quantization including Blackbody radiation Photoelectric effect Compton scattering X-rays and their spectra We ll see how early
More informationChapter 27 Early Quantum Theory and Models of the Atom Discovery and Properties of the electron
Chapter 27 Early Quantum Theory and Models of the Atom 27-1 Discovery and Properties of the electron Measure charge to mass ratio e/m (J. J. Thomson, 1897) When apply magnetic field only, the rays are
More informationQuantum Mechanics. An essential theory to understand properties of matter and light. Chemical Electronic Magnetic Thermal Optical Etc.
Quantum Mechanics An essential theory to understand properties of matter and light. Chemical Electronic Magnetic Thermal Optical Etc. Fall 2018 Prof. Sergio B. Mendes 1 CHAPTER 3 Experimental Basis of
More informationPart I. Quantum Mechanics. 2. Is light a Wave or Particle. 3a. Electromagnetic Theory 1831 Michael Faraday proposes Electric and Magnetic Fields
Quantized Radiation (Particle Theory of Light) Dr. Bill Pezzaglia Part I 1 Quantum Mechanics A. Classical vs Quantum Theory B. Black Body Radiation C. Photoelectric Effect 2 Updated: 2010Apr19 D. Atomic
More informationParticle nature of light & Quantization
Particle nature of light & Quantization A quantity is quantized if its possible values are limited to a discrete set. An example from classical physics is the allowed frequencies of standing waves on a
More informationCHAPTER 27 Quantum Physics
CHAPTER 27 Quantum Physics Units Discovery and Properties of the Electron Planck s Quantum Hypothesis; Blackbody Radiation Photon Theory of Light and the Photoelectric Effect Energy, Mass, and Momentum
More informationE n = n h ν. The oscillators must absorb or emit energy in discrete multiples of the fundamental quantum of energy given by.
Planck s s Radiation Law Planck made two modifications to the classical theory The oscillators (of electromagnetic origin) can only have certain discrete energies determined by E n = n h ν with n is an
More informationExplain how Planck resolved the ultraviolet catastrophe in blackbody radiation. Calculate energy of quanta using Planck s equation.
Objectives Explain how Planck resolved the ultraviolet catastrophe in blackbody radiation. Calculate energy of quanta using Planck s equation. Solve problems involving maximum kinetic energy, work function,
More informationis the minimum stopping potential for which the current between the plates reduces to zero.
Module 1 :Quantum Mechanics Chapter 2 : Introduction to Quantum ideas Introduction to Quantum ideas We will now consider some experiments and their implications, which introduce us to quantum ideas. The
More informationThe Photoelectric Effect
Stellar Astrophysics: The Interaction of Light and Matter The Photoelectric Effect Methods of electron emission Thermionic emission: Application of heat allows electrons to gain enough energy to escape
More informationSparks in Gases: Line Spectra
Lecture 11 February 4, Chapter 3 The Particlelike Properties of Electromagnetic Radiation Sparks in Gases: Line Spectra This is one of the oldest tools available for the investigation of atoms and radiation.
More information2. Fingerprints of Matter: Spectra
2. Fingerprints of Matter: Spectra 2.1 Measuring spectra: prism and diffraction grating Light from the sun: white light, broad spectrum (wide distribution) of wave lengths. 19th century: light assumed
More informationProperties of Electromagnetic Radiation Chapter 5. What is light? What is a wave? Radiation carries information
Concepts: Properties of Electromagnetic Radiation Chapter 5 Electromagnetic waves Types of spectra Temperature Blackbody radiation Dual nature of radiation Atomic structure Interaction of light and matter
More informationPreview. Atomic Physics Section 1. Section 1 Quantization of Energy. Section 2 Models of the Atom. Section 3 Quantum Mechanics
Atomic Physics Section 1 Preview Section 1 Quantization of Energy Section 2 Models of the Atom Section 3 Quantum Mechanics Atomic Physics Section 1 TEKS The student is expected to: 8A describe the photoelectric
More informationLine Spectra / Spectroscopy Applications to astronomy / astrophysics
Line Spectra / Spectroscopy Applications to astronomy / astrophysics Line Spectra With d: distance between slits. It is observed that chemical elements produce unique colors when burned (with a flame)
More informationLIGHT. Question. Until very recently, the study of ALL astronomical objects, outside of the Solar System, has been with telescopes observing light.
LIGHT Question Until very recently, the study of ALL astronomical objects, outside of the Solar System, has been with telescopes observing light. What kind of information can we get from light? 1 Light
More informationChapter One. The Old Quantum Theory. 1-1 Why Quantum Mechanics.
Chapter One The Old Quantum Theory 1-1 Why Quantum Mechanics. The birth of quantum mechanics can be dated to 1925, when physicists such as Werner Heisenberg and Erwin Schrödinger invented mathematical
More informationModern Physics (Lec. 1)
Modern Physics (Lec. 1) Physics Fundamental Science Concerned with the fundamental principles of the Universe Foundation of other physical sciences Has simplicity of fundamental concepts Divided into five
More informationAnnouncements. A test of General Relativity. Gravitational Radiation. Other Consequences of GR
Announcements HW1: Ch.2-70, 75, 76, 87, 92, 97, 99, 104, 111 *** Lab start-up meeting with TA This Week *** Lab manual is posted on the course web *** Course Web Page *** http://highenergy.phys.ttu.edu/~slee/2402/
More informationHistorical Background of Quantum Mechanics
Historical Background of Quantum Mechanics The Nature of Light The Structure of Matter Dr. Sabry El-Taher 1 The Nature of Light Dr. Sabry El-Taher 2 In 1801 Thomas Young: gave experimental evidence for
More informationIntroduction to Modern Physics NE 131 Physics for Nanotechnology Engineering
Introduction to Modern Physics NE 131 Physics for Nanotechnology Engineering Dr. Jamie Sanchez-Fortún Stoker Department of Physics, University of Waterloo Fall 2005 1 Introduction to Modern Physics 1.1
More informationQM all started with - - The Spectrum of Blackbody Radiation
QM all started with - - The Spectrum of Blackbody Radiation Thermal Radiation: Any object, not at zero temperature, emits electromagnetic called thermal. When we measure the intensity of a real object,
More informationQuantum and Atomic Physics - Multiple Choice
PSI AP Physics 2 Name 1. The Cathode Ray Tube experiment is associated with: (A) J. J. Thomson (B) J. S. Townsend (C) M. Plank (D) A. H. Compton 2. The electron charge was measured the first time in: (A)
More informationChapter 38. The End of Classical Physics
Chapter 38. The End of Classical Physics Studies of the light emitted by gas discharge tubes helped bring classical physics to an end. Chapter Goal: To understand how scientists discovered the properties
More informationEarly Quantum Theory and Models of the Atom
Early Quantum Theory and Models of the Atom Electron Discharge tube (circa 1900 s) There is something ( cathode rays ) which is emitted by the cathode and causes glowing Unlike light, these rays are deflected
More informationModule 5 : MODERN PHYSICS Lecture 23 : Particle and Waves
Module 5 : MODERN PHYSICS Lecture 23 : Particle and Waves Objectives In this lecture you will learn the following Radiation (light) exhibits both wave and particle nature. Laws governing black body radiation,
More informationRadiation - Electromagnetic Waves (EMR): wave consisting of oscillating electric and magnetic fields that move at the speed of light through space.
Radiation - Electromagnetic Waves (EMR): wave consisting of oscillating electric and magnetic fields that move at the speed of light through space. Photon: a quantum of light or electromagnetic wave. Quantum:
More informationQuantum Mechanics: Blackbody Radiation
Blackbody Radiation Quantum Mechanics Origin of Quantum Mechanics Raleigh-Jeans law (derivation)-ultraviolet catastrophe, Wien s Distribution Law & Wein s Displacement law, Planck s radiation law (calculation
More information1. Historical perspective
Atomic and Molecular Physics/Lecture notes presented by Dr. Fouad Attia Majeed/Third year students/college of Education (Ibn Hayyan)/Department of Physics/University of Babylon. 1. Historical perspective
More informationPhotoelectric Effect & Bohr Atom
PH0008 Quantum Mechanics and Special Relativity Lecture 03 (Quantum Mechanics) 020405v2 Photoelectric Effect & Bohr Atom Prof Department of Physics Brown University Main source at Brown Course Publisher
More informationStellar Astrophysics: The Continuous Spectrum of Light
Stellar Astrophysics: The Continuous Spectrum of Light Distance Measurement of Stars Distance Sun - Earth 1.496 x 10 11 m 1 AU 1.581 x 10-5 ly Light year 9.461 x 10 15 m 6.324 x 10 4 AU 1 ly Parsec (1
More informationAstronomy 1 Winter 2011
Astronomy 1 Winter 2011 Lecture 8; January 24 2011 Previously on Astro 1 Light as a wave The Kelvin Temperature scale What is a blackbody? Wien s law: λ max (in meters) = (0.0029 K m)/t. The Stefan-Boltzmann
More informationDual Nature of Radiation and Matter-I
Dual Nature of Radiation and Matter-I Physics Without Fear CONTENTS ELECTRON EMISSION PHOTOELECTRIC EFFECT; HERTZ S OBSERVATIONS HALLWACHS AND LENARD S OBSERVATIONS EXPERIMENTAL STUDY OF PHOTOELECTRIC
More informationThe Experimental Basis of Quantum Physics
Chapter 2. The Experimental Basis of Quantum Physics Notes: Most of the material in this chapter is taken from Thornton and Rex, Chapter 3, and The Feynman Lectures on Physics, Vol. I by R. P. Feynman,
More information4. The discovery of X-rays and electrons 4.1 Gas discharges
4. The discovery of X-rays and electrons 4.1 Gas discharges 19 th century: knowledge of charged atoms/molecules electrolysis discharges of rarefied gases (vacuum). near cathode: glow charge, cathode rays
More informationThe term "black body" was introduced by Gustav Kirchhoff in The light emitted by a black body is called black-body radiation.
Black body (Redirected from Black-body radiation) As the temperature decreases, the peak of the black body radiation curve moves to lower intensities and longer wavelengths. The black-body radiation graph
More informationChapter 37 Early Quantum Theory and Models of the Atom
Chapter 37 Early Quantum Theory and Models of the Atom Units of Chapter 37 37-7 Wave Nature of Matter 37-8 Electron Microscopes 37-9 Early Models of the Atom 37-10 Atomic Spectra: Key to the Structure
More informationPlanck s Quantum Hypothesis Blackbody Radiation
Planck s Quantum Hypothesis Blackbody Radiation The spectrum of blackbody radiation has been measured(next slide); it is found that the frequency of peak intensity increases linearly with temperature.
More informationChapter 9: Quantization of Light
Chapter 9: Quantization of Light Max Planck started the revolution of quantum theory by challenging the classical physics and the classical wave theory of light. He proposed the concept of quantization
More informationChapter 28. Atomic Physics
Chapter 28 Atomic Physics Sir Joseph John Thomson J. J. Thomson 1856-1940 Discovered the electron Did extensive work with cathode ray deflections 1906 Nobel Prize for discovery of electron Early Models
More informationThe Nature of Light. Chapter Five
The Nature of Light Chapter Five Guiding Questions 1. How fast does light travel? How can this speed be measured? 2. Why do we think light is a wave? What kind of wave is it? 3. How is the light from an
More informationLecture 8. > Blackbody Radiation. > Photoelectric Effect
Lecture 8 > Blackbody Radiation > Photoelectric Effect *Beiser, Mahajan & Choudhury, Concepts of Modern Physics 7/e French, Special Relativity *Nolan, Fundamentals of Modern Physics 1/e Serway, Moses &
More informationLecture PowerPoints. Chapter 27 Physics: Principles with Applications, 7th edition Giancoli
Lecture PowerPoints Chapter 27 Physics: Principles with Applications, 7th edition Giancoli This work is protected by United States copyright laws and is provided solely for the use of instructors in teaching
More informationTopics Covered in Chapter. Light and Other Electromagnetic Radiation. A Subatomic Interlude II. A Subatomic Interlude. A Subatomic Interlude III
Light and Other Electromagnetic Radiation Topics Covered in Chapter 1.Structure of Atoms 2.Origins of Electromagnetic Radiation 3.Objects with Different Temperature and their Electromagnetic Radiation
More informationLight and Other Electromagnetic Radiation
Light and Other Electromagnetic Radiation 1 Topics Covered in Chapter 1.Structure of Atoms 2.Origins of Electromagnetic Radiation 3.Objects with Different Temperature and their Electromagnetic Radiation
More informationRED. BLUE Light. Light-Matter
1 Light-Matter This experiment demonstrated that light behaves as a wave. Essentially Thomas Young passed a light of a single frequency ( colour) through a pair of closely spaced narrow slits and on the
More informationChapter 37 Early Quantum Theory and Models of the Atom. Copyright 2009 Pearson Education, Inc.
Chapter 37 Early Quantum Theory and Models of the Atom Planck s Quantum Hypothesis; Blackbody Radiation Photon Theory of Light and the Photoelectric Effect Energy, Mass, and Momentum of a Photon Compton
More informationNOTES: 5.3 Light and Atomic Spectra (more Quantum Mechanics!)
NOTES: 5.3 Light and Atomic Spectra (more Quantum Mechanics!) Light WAVE or PARTICLE? Electromagnetic Radiation Electromagnetic radiation includes: -radio waves -microwaves -infrared waves -visible light
More informationGeneral Physics (PHY 2140)
General Physics (PHY 2140) Lecture 27 Modern Physics Quantum Physics Blackbody radiation Plank s hypothesis http://www.physics.wayne.edu/~apetrov/phy2140/ Chapter 27 1 Quantum Physics 2 Introduction: Need
More informationAnnouncements. Fast => v~c c= the velocity of light
Announcements 2402 Lab will be started this week Lab manual is available on the course web page HW: Chapter.2 70, 75, 76, 87, 92, 97*, 99, 104, 111 1 st Quiz: 9/18 (Ch.2) Nonclassical Physics *** Course
More informationThe Nature of Light I: Electromagnetic Waves Spectra Kirchoff s Laws Temperature Blackbody radiation
The Nature of Light I: Electromagnetic Waves Spectra Kirchoff s Laws Temperature Blackbody radiation Electromagnetic Radiation (How we get most of our information about the cosmos) Examples of electromagnetic
More informationPSI AP Physics How was it determined that cathode rays possessed a negative charge?
PSI AP Physics 2 Name Chapter Questions 1. How was it determined that cathode rays possessed a negative charge? 2. J. J. Thomson found that cathode rays were really particles, which were subsequently named
More informationSTSF2223 Quantum Mechanics I
STSF2223 Quantum Mechanics I What is quantum mechanics? Why study quantum mechanics? How does quantum mechanics get started? What is the relation between quantum physics with classical physics? Where is
More informationQuantum physics (quantum theory, quantum mechanics) Part 1
Quantum physics (quantum theory, quantum mechanics) Part 1 1 Outline Introduction Problems of classical physics Black-body Radiation experimental observations Wien s displacement law Stefan Boltzmann law
More informationChapter 27. Quantum Physics
Chapter 27 Quantum Physics Need for Quantum Physics Problems remained from classical mechanics that relativity didn t explain Blackbody Radiation The electromagnetic radiation emitted by a heated object
More informationLecture 2 Blackbody radiation
Lecture 2 Blackbody radiation Absorption and emission of radiation What is the blackbody spectrum? Properties of the blackbody spectrum Classical approach to the problem Plancks suggestion energy quantisation
More informationSemiconductor Physics and Devices
Introduction to Quantum Mechanics In order to understand the current-voltage characteristics, we need some knowledge of electron behavior in semiconductor when the electron is subjected to various potential
More informationBlackbody Radiation. Rayleigh-Jeans law was an attempt to explain blackbody radiation based on classical ideas:
Blackbody Radiation A Blackbody is an ideal system that absorbs all radiation incident on it. Emission of radiation by a blackbody is independent of the properties of its wall, but depends only on its
More information12 - DUAL NATURE OF RADIATION AND MATTER Page 1
1 - DUAL NATURE OF RADIATION AND MATTER Page 1 1.1 Birth of Modern Physics By 1880, most physicists thought that important laws in physics were already discovered and all that remained was their refined
More informationQuantum Physics and Atomic Models Chapter Questions. 1. How was it determined that cathode rays possessed a negative charge?
Quantum Physics and Atomic Models Chapter Questions 1. How was it determined that cathode rays possessed a negative charge? 2. J. J. Thomson found that cathode rays were really particles, which were subsequently
More information1 The Cathode Rays experiment is associated. with: Millikan A B. Thomson. Townsend. Plank Compton
1 The Cathode Rays experiment is associated with: A B C D E Millikan Thomson Townsend Plank Compton 1 2 The electron charge was measured the first time in: A B C D E Cathode ray experiment Photoelectric
More informationChapter 1. From Classical to Quantum Mechanics
Chapter 1. From Classical to Quantum Mechanics Classical Mechanics (Newton): It describes the motion of a classical particle (discrete object). dp F ma, p = m = dt dx m dt F: force (N) a: acceleration
More informationChapter 1 Early Quantum Phenomena
Chapter Early Quantum Phenomena... 8 Early Quantum Phenomena... 8 Photo- electric effect... Emission Spectrum of Hydrogen... 3 Bohr s Model of the atom... 4 De Broglie Waves... 7 Double slit experiment...
More informationASTR-1010: Astronomy I Course Notes Section IV
ASTR-1010: Astronomy I Course Notes Section IV Dr. Donald G. Luttermoser Department of Physics and Astronomy East Tennessee State University Edition 2.0 Abstract These class notes are designed for use
More informationDual Nature of Matter and Radiation 9. The work function of a certain metal is 3.3 J. Then the maximum kinetic energy of photoelectrons emitted by incident radiation of wavelength 5 A is- ).48 ev ).4 ev
More informationLECTURE # 19 Dennis Papadopoulos End of Classical Physics Quantization Bohr Atom Chapters 38 39
PHYS 270-SPRING 2011 LECTURE # 19 Dennis Papadopoulos End of Classical Physics Quantization Bohr Atom Chapters 38 39 April 14, 2011 1 HOW TO MEASURE SPECTRA Spectroscopy: Unlocking the Structure of Atoms
More informationChapter 38. Photons Light Waves Behaving as Particles
Chapter 38 Photons Light Waves Behaving as Particles 38.1 The Photoelectric Effect The photoelectric effect was first discovered by Hertz in 1887, and was explained by Einstein in 1905. The photoelectric
More informationThe birth of atomic physics and quantum mechanics. Honors Physics Don Rhine
The birth of atomic physics and quantum mechanics Honors Physics Don Rhine Constants & Atomic Data Look inside back cover of book! Speed of Light (vacuum): c = 3.00 x 10 8 m/s Elementary Charge: e - =
More informationAnnouncements. Some Examples. Lecture 6 Chapter. 2 Special Relativity. Relativistic Dynamics. Problems. Problems
Announcements HW2: Ch.2-70, 75, 76, 87, 92, 97, 99, 104, 111 HW1 die: now, HW2 due: 2/9 (by class hour) How was your 1 st Lab? -- Any question? Lab manual is posted on the course web *** Course Web Page
More informationProblems with Classical Physics. Blackbody Radiation Photoelectric Effect Compton Effect Bohr Model of Atom
The Quantum Gang Problems with Classical Physics Blackbody Radiation Photoelectric Effect Compton Effect Bohr Model of Atom Why this shape? Why the drop? Blackbody Radiation A black body is an ideal system
More informationChapter 28. Atomic Physics
Chapter 28 Atomic Physics Quantum Numbers and Atomic Structure The characteristic wavelengths emitted by a hot gas can be understood using quantum numbers. No two electrons can have the same set of quantum
More informationAstronomy The Nature of Light
Astronomy The Nature of Light A. Dayle Hancock adhancock@wm.edu Small 239 Office hours: MTWR 10-11am Measuring the speed of light Light is an electromagnetic wave The relationship between Light and temperature
More informationQuantum Mechanics (made fun and easy)
Lecture 7 Quantum Mechanics (made fun and easy) Why the world needs quantum mechanics Why the world needs quantum mechanics Why the world needs quantum mechanics Why the world needs quantum mechanics Why
More informationDUAL NATURE OF RADIATION AND MATTER I K GOGIA KV JHARODA KALAN DELHI.
DUAL NATURE OF RADIATION AND MATTER AIM: The aim of present self- learning module is to train the minds of the learners in building the concepts by learning on their own. The module is designed to Achieve
More informationExam 2 Development of Quantum Mechanics
PHYS40 (Spring 00) Riq Parra Exam # (Friday, April 1 th, 00) Exam Development of Quantum Mechanics Do NOT write your name on this exam. Write your class ID number on the top right hand corner of each problem
More informationParticle Wave Duality. What is a particle? What is a wave?
Particle Wave Duality What is a particle? What is a wave? Problems with Classical Physics Nature of Light? Discrete Spectra? Blackbody Radiation? Photoelectric Effect? Compton Effect? Model of Atom? Thomas
More informationModern Physics, summer Modern physics. Historical introduction to quantum mechanics
1 Modern physics 2 Gustav Kirchhoff (1824-1887) Surprisingly, the path to quantum mechanics begins with the work of German physicist Gustav Kirchhoff in 1859. Electron was discovered by J.J.Thomson in
More informationChapter 7. Quantum Theory and Atomic Structure
Chapter 7 Quantum Theory and Atomic Structure Outline 1. The Nature of Light 2. Atomic Spectra 3. The Wave-Particle Duality of Matter and Energy 4. The Quantum-Mechanical Model of the Atom 3 September
More informationChapter 7: The Quantum-Mechanical Model of the Atom
C h e m i s t r y 1 A : C h a p t e r 7 P a g e 1 Chapter 7: The Quantum-Mechanical Model of the Atom Homework: Read Chapter 7. Work out sample/practice exercises Check for the MasteringChemistry.com assignment
More informationThe Duality of Light. Electromagnetic Radiation. Light as a Wave
In this unit, you will be introduced to the dual nature of light, the quantum theory and Bohr s planetary atomic model. The planetary model was an improvement on the nuclear model and attempted to answer
More informationB. Sc. Physics (H.R.K) Chapter 49: Light and Quantum Physics LIGHT AND QUANTUM PHYSICS
LIGHT AND QUANTUM PHYSICS 49.1 Thermal Radiations The radiations emitted by a body due to its temperature are called thermal radiations. All bodies not only emit the thermal radiations, but also absorb
More informationQuantum Mysteries. Scott N. Walck. September 2, 2018
Quantum Mysteries Scott N. Walck September 2, 2018 Key events in the development of Quantum Theory 1900 Planck proposes quanta of light 1905 Einstein explains photoelectric effect 1913 Bohr suggests special
More informationQUANTUM MECHANICS Chapter 12
QUANTUM MECHANICS Chapter 12 Colours which appear through the Prism are to be derived from the Light of the white one Sir Issac Newton, 1704 Electromagnetic Radiation (prelude) FIG Electromagnetic Radiation
More informationAtomic Physics and Lasers. The idea of a photon. Light from a hot object... Example of a Blackbody. Example of a Blackbody
Atomic Physics and Lasers The idea of a photon Black body radiation Photoelectric Effect The structure of the atom How does a Laser work? Interaction of lasers with matter Laser safety Applications Spectroscopy,
More informationQuantum Model Einstein s Hypothesis: Photoelectric Effect
VISUAL PHYSICS ONLINE MODULE 7 NATURE OF LIGHT Quantum Model Einstein s Hypothesis: Photoelectric Effect The photoelectric effect was discovered by Hertz in 1887 as he confirmed Maxwell s electromagnetic
More informationAP Physics Study Guide Modern Physics I. Atomic Physics and Quantum Effects 1. Who is generally credited with the discovery of the electron?
AP Physics Study Guide Modern Physics I. Atomic Physics and Quantum Effects 1. Who is generally credited with the discovery of the electron? 2. What was it that J. J. Thomson actually measured? 3. Regarding
More informationChapter 27. Quantum Physics
Chapter 27 Quantum Physics Need for Quantum Physics Problems remained from classical mechanics that relativity didn t explain Blackbody Radiation The electromagnetic radiation emitted by a heated object
More informationThe atom cont. +Investigating EM radiation
The atom cont. +Investigating EM radiation Announcements: First midterm is 7:30pm on Sept 26, 2013 Will post a past midterm exam from 2011 today. We are covering Chapter 3 today. (Started on Wednesday)
More informationConstants & Atomic Data. The birth of atomic physics and quantum mechanics. debroglie s Wave Equations. Energy Calculations. λ = f = h E.
Constants & Atomic Data The birth of atomic physics and quantum mechanics Honors Physics Don Rhine Look inside back cover of book! Speed of Light (): c = 3.00 x 10 8 m/s Elementary Charge: e - = p + =
More informationSECTION A Quantum Physics and Atom Models
AP Physics Multiple Choice Practice Modern Physics SECTION A Quantum Physics and Atom Models 1. Light of a single frequency falls on a photoelectric material but no electrons are emitted. Electrons may
More informationRevision Guide. Chapter 7 Quantum Behaviour
Revision Guide Chapter 7 Quantum Behaviour Contents CONTENTS... 2 REVISION CHECKLIST... 3 REVISION NOTES... 4 QUANTUM BEHAVIOUR... 4 Random arrival of photons... 4 Photoelectric effect... 5 PHASE AN PHASORS...
More informationAST 105 Intro Astronomy The Solar System. MIDTERM II: Tuesday, April 5 [covering Lectures 10 through 16]
AST 105 Intro Astronomy The Solar System MIDTERM II: Tuesday, April 5 [covering Lectures 10 through 16] REVIEW Light as Information Bearer We can separate light into its different wavelengths (spectrum).
More informationChapter 27 Quantum Physics
Key Ideas Two Principles of Relativity: The laws of physics are the same for all uniformly moving observers. The speed of light is the same for all observers. Consequences: Different observers measure
More information5. Light-matter interactions: Blackbody radiation
5. Light-matter interactions: Blackbody radiation The electromagnetic spectrum Sources of light Boltzmann's Law Blackbody radiation why do hot things glow? The cosmic microwave background The electromagnetic
More information