Lecture 2 Blackbody radiation

Size: px
Start display at page:

Download "Lecture 2 Blackbody radiation"

Transcription

1 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 Bose-Einstein statistics

2 Objectives Learn how classical theories cannot account for the spectral distribution of light from blackbody objects such as stars etc. Show that by making the assumption that light consists of small packets of energy (photons) we can develop an expression which perfectly fits the experimental data.

3 Blackbody radiation Heated bodies radiate energy, but what is the mechanism? On an atomic scale, heat causes the molecules and atoms of a solid to vibrate. As atoms consist of electrical charges in the form of electrons and protons, it is the vibration of these charges which is responsible for the emission of electromagnetic radiation. A very hot object will emit visible light as the electrons vibrate. How do bodies absorb radiation? In order to radiate energy, an object must first absorb it. Suppose we shine a light on an object. If we shine it on glass Light passes through If we shine it on a metal Light is reflected If we shine it on carbon Light is absorbed In glass the electrons are tightly bound to atoms and only oscillate at certain frequencies outside the range of visible light. This makes glass appear transparent as very little of the visible light is absorbed.

4 Blackbody radiation II Metals conduct and have free electrons not bound to any particular atom. These electrons oscillate in response to the light and then radiate light themselves. This radiation is reflected light. Again, there is very little absorption of light, most of it is reflected. The electrons in carbon have a short mean free path, when they collide their energy is transferred to the lattice. They are efficient absorbers of the incident light, hence carbon appears black. Carbon and similar materials are effective at converting incident light into heat. In a reverse process, as the carbon atoms warm up and vibrate more vigorously, more of the lattice energy is transferred to the free electrons, thus carbon is also a good radiator of heat. It cools down much faster than a metal as it is more efficient at converting the lattice energy into radiation.

5 Measuring the distribution of emitted radiation A simple spectroscope If we pass white light through a prism we obtain a spectrum. By measuring the intensity of each wavelength of light in the spectrum we can plot the spectral distribution.

6 The blackbody spectrum Consider a box with a small hole in the side. Radiation entering the hole is scattered inside the box and only a small amount comes out again. If the temperature of the box is in equilibrium the spectrum of light coming out of the hole looks something like this. 2.0x10-8 U(f) (arb. units) 1.5x x x T = 3000K T = 6000K 0.5x x x x10 15 Frequency (Hz) Typical blackbody spectra U f = Intensity of radiation of frequency f. We find similar spectral distributions if we measure the light from stars.

7 From red hot to white hot The colour of a hot object changes as the temperature increases

8 Properties of the blackbody spectrum For small f, U is proportional to f 2. But at some value of f there is a peak before U falls to zero. If we double the temperature the position of the peak doubles in frequency ( f peak T ) (Wien s displacement law), however the height of the peak is multiplied eight times. Why? U f 2 so if the temperature is constant U 2 f =4 U f, but we doubled the temperature so in fact U 2T =8U T. The total energy radiated by the body, the area under the curve, increases by a factor of 16, i.e 2 4 times more, when the temperature is doubled. Stefans law of radiation: U = T 4, = W/m 2 /K 4 - Stefans constant. U is the energy radiated from 1m 2 of black surface at temperature T.

9 Wien s displacement law f peak =at or peak T =b, b = mk (Wien s displacement law). For frequency f peak =2.82 k B T / h. k B = Boltzmann s constant = J/K. Note that f peak peak c.

10 Relationship between emitted radiation and radiation inside the cavity The energy (electromagnetic radiation) comes out of the hole at a speed c. Some of the light comes out at an angle and the hole appears smaller. Emitted radiation = R, radiation inside the cavity = P c m 2 /2 R= 0 0 cp cos θ d 4, d =sin θ d d θ A = cos θ P θ 2 /2 R= cp cos θ sin θ d d θ= cp 0 8 d = cp 4 Energy incident at an angle θ on a hole of unit area. So R=cP /4. The energy emitted from the hole is representative of the energy inside the cavity.

11 Origins of the spectrum The energy spectrum is formed by a continuous process of absorption and re-emission of radiation by the atoms and molecules forming the walls of the box. In this way the energy can shift from one mode to another. When thermal equilibrium is reached the characteristic spectrum will be established. To form a theoretical description of the spectrum we need to determine how many modes of oscillation have frequencies in a given energy range. These oscillators are the electromagnetic waves inside the box, which can be thought of as standing waves.

12 Modes in a box The electric field at the cavity wall must be zero

13 Standing waves I Pluck a string n=1 n=2 n=3 n=4 n 2 =L The natural modes of vibration of the string are standing waves with nodes at the ends. In the same way, electromagnetic waves inside the box are also standing waves.

14 Standing waves II 1.0 Amplitude n=1 n=2 n= Position (x/a) (arb. units) Standing waves inside a cavity of length a. The standing waves have amplitude y=a sin(2 π x / λ)cos(2 π f t ). Let k=2 /, and =2 f then y=a sin(kx)cos(ωt). If the box has sides of length a then a=n /2 for n =1,2,3 The frequencies of these waves are f =c/ =n c/ 2 a. So k=n /a and =ck.

15 K space We can represent the standing waves in 3D space by a set of k vectors k= k x, k y, k z = a l,m,n. Each point can be associated with a cubic volume of space and represents a frequency of =ck=c k x 2 k y 2 k z 2, the volume of the associated space is 3 / a 3. For a fixed frequency,, we obtain a set of values for k x, k y and k z which lie on a spherical surface: 2 c =k 2 2 x k 2 y k 2 z with radius k= /c. To get the total number of vibrational modes in the frequency range zero to we count the number of cubes contained in the sphere with radius k= /c. N cubes =Volume between spheres / volume of cube.

16 K-space II Each mode occupies a discrete volume of K-space.

17 Mode counting The volume of the whole sphere is 4 k 3 /3, but we are limited to positive values of k, i.e. one octant of the sphere, so the volume becomes V s = k 3 = k Now k 3 = 3 c 3 and =2 f so k 3 = 8 3 f 3 c 3. If V cube = 3 / a 3, the total number of cubes, N, is V s /V cube, so N = 8 f 3 a 3. 6 c 3 Putting, V =a 3, differentiating with respect to f, and multiplying by two because we can have two orthogonal transverse electromagnetic waves at each frequency we get N f = 8 f 2 V. df c 3

18 Comparison with experiment In the classical approach we assign each mode an energy k B T. The total energy emitted at each frequency from a box of unit volume is given by N f k B T =U RJ f = 8 f 2 c 3 k B T. This is the Rayleigh-Jeans approximation (1900). k B is Boltzmann s constant = J/K. We find good agreement between the Rayleigh-Jeans equation and the observed results for low values of f, i.e. where U f f 2. The higher the temperature the bigger the frequency range over which the agreement is good. Doubling the temperature doubles the energy output at low frequencies, as expected from the proportionality to T. However, at higher frequencies the experimental and theoretical results diverge. We expect more energy to be output at higher frequencies, but in experiments the energy distribution falls to zero. This failure of the Reyleigh-Jeans model is sometimes called the UV catastrophe.

19 Planck s suggestion Planck suggested that energy could only be emitted in chunks that are multiples of hf, where h is Planck s constant ( Js). Experimentally, we can see this reflected in the fact that f peak T. By doubling the temperature the number of modes that can radiate freely is also doubled. From this explanation it is clear that if the average energy per mode is k B T and the value hf for a particular mode is, e.g., 5 k B T, that mode will be unlikely to radiate. As the frequency increases, the probability of radiation decreases. Replacing U =k B T with U =hf in the Rayleigh-Jeans equation gives U Planck f = 8 f 2 hf P BE f, where P BE f is the Bose-Einstein factor for c 3 the average number of photons per mode at frequency f. hf P BE f is the average energy, E, of photons with frequency f.

20 The Bose-Einstein factor We assume that the probability of occupying an energy level E is given by P E = e E /k B T. This was proved by Planck. N 3 E 3 = 3hf P 3 = Aexp(-3hf/k B T) N 1 =N 0 e hf / k B T N 2 N 1 E 2 = 2hf E 1 = hf P 2 = Aexp(-2hf/k B T) P 1 = Aexp(-hf/k B T) N 2 =N 0 e 2hf / k B T N 0 E 0 = 0 P 0 = A Energy levels of a quantum oscillator N n =N 0 e nhf / k B T Let x=hf / k B T, then N 1 =N 0 e x, N 2 =N 0 e 2x, so N Total =N 0 1 e x e 2x.... E n =N n nhf = N 0 e nx nhf = N 0 hf ne nx and E Total =N 0 hf 0 e x 2 e 2x....

21 The Bose-Einstein factor II The average energy is given by E = E N 0 hf Total n = N Total N 0 n ne nx e nx =hfp BE f ne nx n P BE f = n e = d nx dx log n e nx = d dx log 1 1 e x = 1 e x 1 = 1 e hf / k B T 1 So our final result is U Planck f = 8 f 2 c 3 hf e hf /k B T 1. Even though this is proportional to f 3 the Bose-Einstein term reduces the energy to zero at high frequencies. At low frequencies the term on the right approximates to 1, matching the Rayleigh-Jeans approximation. As f 0 or T the average energy approaches k B T, the same as the classical result.

22 Various blackbody spectra

23 Conclusions Classical physics, in which electromagnetic radiation is assumed to be a continuous wave, cannot account for the blackbody radiation spectrum. The assumption that electromagnetic radiation is emitted in quanta with energy E =hf allows us to develop an expression which accurately describes the spectral distribution of radiation emitted from a blackbody.

Module 5 : MODERN PHYSICS Lecture 23 : Particle and Waves

Module 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 information

Class 11: Thermal radiation

Class 11: Thermal radiation Class : Thermal radiation By analyzing the results from a number of eperiments, Planck found the energy density of the radiation emitted by a black body in wavelength interval (, d + was well described

More information

The term "black body" was introduced by Gustav Kirchhoff in The light emitted by a black body is called black-body radiation.

The 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 information

5. Light-matter interactions: Blackbody radiation

5. Light-matter interactions: Blackbody radiation 5. Light-matter interactions: Blackbody radiation REMINDER: no lecture on Monday Feb. 6th The electromagnetic spectrum Sources of light Boltzmann's Law Blackbody radiation The cosmic microwave background

More information

Quantum Physics Lecture 6

Quantum Physics Lecture 6 Quantum Physics Lecture 6 Thermal Phenomena Specific Heats - Classical model, failure at low temperature - Einstein model Black Body radiation - Classical model, UV catastrophe - Planck model - Wien &

More information

QM all started with - - The Spectrum of Blackbody Radiation

QM 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 information

Satish Chandra. Blackbody. Unit IV, BLACK BODY RADIATION. Radiation in a Hollow Enclosure. Pure Temperature Dependence

Satish Chandra. Blackbody. Unit IV, BLACK BODY RADIATION. Radiation in a Hollow Enclosure. Pure Temperature Dependence Lecture Notes Dated: Jan 04, 013 Blackbody The ability of a body to radiate is closely related to its ability to absorb radiation. This is to be expected, since a body at a constant temperature is in thermal

More information

Physics 2D Lecture Slides Lecture 10. Jan.25, 2010

Physics 2D Lecture Slides Lecture 10. Jan.25, 2010 Physics 2D Lecture Slides Lecture 10 Jan.25, 2010 Radiation from A Blackbody (a) Intensity of Radiation I =! R (#) d# " T 4 I =! T 4 (Area under curve) Stephan-Boltzmann Constant σ = 5.67 10-8 W / m 2

More information

Black Body Radiation. Heated Bodies Radiate. How is Radiation Absorbed? Absorption and Emission. Observing the Black Body Spectrum.

Black Body Radiation. Heated Bodies Radiate. How is Radiation Absorbed? Absorption and Emission. Observing the Black Body Spectrum. Black Body Radiation Michael Fowler University of Virginia Physics 252 Home Page Link to Previous Lecture Link to Next Lecture Heated Bodies Radiate We shall now turn to another puzzle confronting physicists

More information

Quantum Mechanics: Blackbody Radiation

Quantum 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 information

5. Light-matter interactions: Blackbody radiation

5. 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

Quantum Physics Lecture 5

Quantum Physics Lecture 5 Quantum Physics Lecture 5 Thermal Phenomena - continued Black Body radiation - Classical model, UV catastrophe - Planck model, Wien & Stefan laws - Photoelectric effect revisited The hydrogen atom Planetary

More information

Blackbody Radiation. Rayleigh-Jeans law was an attempt to explain blackbody radiation based on classical ideas:

Blackbody 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 information

Physics 1C. Lecture 27A

Physics 1C. Lecture 27A Physics 1C Lecture 27A "Any other situation in quantum mechanics, it turns out, can always be explained by saying, You remember the experiment with the two holes? It s the same thing. " --Richard Feynman

More information

Determination of Stefan-Boltzmann Constant.

Determination of Stefan-Boltzmann Constant. Determination of Stefan-Boltzmann Constant. An object at some non-zero temperature radiates electromagnetic energy. For the perfect black body, which absorbs all light that strikes it, it radiates energy

More information

Sources of radiation

Sources of radiation Sources of radiation Most important type of radiation is blackbody radiation. This is radiation that is in thermal equilibrium with matter at some temperature T. Lab source of blackbody radiation: hot

More information

Modern Physics (Lec. 1)

Modern 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 information

Properties of Electromagnetic Radiation Chapter 5. What is light? What is a wave? Radiation carries information

Properties 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 information

Early Quantum Theory and Models of the Atom

Early 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 information

Atomic 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. 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 information

2. Fingerprints of Matter: Spectra

2. 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 information

Modern Physics. Unit 1: Classical Models and the Birth of Modern Physics Lecture 1.4: Blackbody Radiation and Photoelectric Effect

Modern Physics. Unit 1: Classical Models and the Birth of Modern Physics Lecture 1.4: Blackbody Radiation and Photoelectric Effect Modern Physics Unit 1: Classical Models and the Birth of Modern Physics Lecture 1.4: Blackbody Radiation and Photoelectric Effect Ron Reifenberger Professor of Physics Purdue University 1 I. Blackbody

More information

is the minimum stopping potential for which the current between the plates reduces to zero.

is 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 information

Modern Physics, summer Modern physics. Historical introduction to quantum mechanics

Modern 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 information

Chapter One. The Old Quantum Theory. 1-1 Why Quantum Mechanics.

Chapter 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 information

Lecture 5: Greenhouse Effect

Lecture 5: Greenhouse Effect /30/2018 Lecture 5: Greenhouse Effect Global Energy Balance S/ * (1-A) terrestrial radiation cooling Solar radiation warming T S Global Temperature atmosphere Wien s Law Shortwave and Longwave Radiation

More information

Lecture 5: Greenhouse Effect

Lecture 5: Greenhouse Effect Lecture 5: Greenhouse Effect S/4 * (1-A) T A 4 T S 4 T A 4 Wien s Law Shortwave and Longwave Radiation Selected Absorption Greenhouse Effect Global Energy Balance terrestrial radiation cooling Solar radiation

More information

Introduction to Modern Physics NE 131 Physics for Nanotechnology Engineering

Introduction 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 information

Lasers PH 645/ OSE 645/ EE 613 Summer 2010 Section 1: T/Th 2:45-4:45 PM Engineering Building 240

Lasers PH 645/ OSE 645/ EE 613 Summer 2010 Section 1: T/Th 2:45-4:45 PM Engineering Building 240 Lasers PH 645/ OSE 645/ EE 613 Summer 2010 Section 1: T/Th 2:45-4:45 PM Engineering Building 240 John D. Williams, Ph.D. Department of Electrical and Computer Engineering 406 Optics Building - UAHuntsville,

More information

Explain how Planck resolved the ultraviolet catastrophe in blackbody radiation. Calculate energy of quanta using Planck s equation.

Explain 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 information

Chapter 4. Spectroscopy. Dr. Tariq Al-Abdullah

Chapter 4. Spectroscopy. Dr. Tariq Al-Abdullah Chapter 4 Spectroscopy Dr. Tariq Al-Abdullah Learning Goals: 4.1 Spectral Lines 4.2 Atoms and Radiation 4.3 Formation of the Spectral Lines 4.4 Molecules 4.5 Spectral Line Analysis 2 DR. T. AL-ABDULLAH

More information

Chapter 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 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 information

ME 476 Solar Energy UNIT TWO THERMAL RADIATION

ME 476 Solar Energy UNIT TWO THERMAL RADIATION ME 476 Solar Energy UNIT TWO THERMAL RADIATION Unit Outline 2 Electromagnetic radiation Thermal radiation Blackbody radiation Radiation emitted from a real surface Irradiance Kirchhoff s Law Diffuse and

More information

Wave Description. Transverse and Longitudinal Waves. Physics Department 2/13/2019. Phys1411 Goderya 1. PHYS 1403 Stars and Galaxies

Wave Description. Transverse and Longitudinal Waves. Physics Department 2/13/2019. Phys1411 Goderya 1. PHYS 1403 Stars and Galaxies PHYS 1403 Stars and Galaxies for Today s Class 1. How do we explain the motion of energy? 2. What is a wave and what are its properties 3. What is an electromagnetic spectrum? 4. What is a black body and

More information

The 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 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 information

Radiation in the Earth's Atmosphere. Part 1: Absorption and Emission by Atmospheric Gases

Radiation in the Earth's Atmosphere. Part 1: Absorption and Emission by Atmospheric Gases Radiation in the Earth's Atmosphere Part 1: Absorption and Emission by Atmospheric Gases Electromagnetic Waves Electromagnetic waves are transversal. Electric and magnetic fields are perpendicular. In

More information

Planck s Hypothesis of Blackbody

Planck s Hypothesis of Blackbody Course : Bsc Applied Physical Science (Computer Science) Year Ist (Sem IInd) Paper title : Thermal Physics Paper No : 6 Lecture no. 20. Planck s Hypothesis of Blackbody Hello friends, in the last lecture

More information

Chemistry 795T. Lecture 7. Electromagnetic Spectrum Black body Radiation. NC State University

Chemistry 795T. Lecture 7. Electromagnetic Spectrum Black body Radiation. NC State University Chemistry 795T Lecture 7 Electromagnetic Spectrum Black body Radiation NC State University Black body Radiation An ideal emitter of radiation is called a black body. Observation: that peak of the energy

More information

Chemistry 795T. Black body Radiation. The wavelength and the frequency. The electromagnetic spectrum. Lecture 7

Chemistry 795T. Black body Radiation. The wavelength and the frequency. The electromagnetic spectrum. Lecture 7 Chemistry 795T Lecture 7 Electromagnetic Spectrum Black body Radiation NC State University Black body Radiation An ideal emitter of radiation is called a black body. Observation: that peak of the energy

More information

Einstein s Approach to Planck s Law

Einstein s Approach to Planck s Law Supplement -A Einstein s Approach to Planck s Law In 97 Albert Einstein wrote a remarkable paper in which he used classical statistical mechanics and elements of the old Bohr theory to derive the Planck

More information

Modern physics. Historical introduction to quantum mechanics

Modern physics. Historical introduction to quantum mechanics 2012-0-08 Modern physics dr hab. inż. Katarzyna ZAKRZEWSKA, prof. AGH KATEDRA ELEKTRONIKI, C-1, office 17, rd floor, phone 617 29 01, mobile phone 0 601 51 5 e-mail: zak@agh.edu.pl, Internet site http://home.agh.edu.pl/~zak

More information

Particle nature of light & Quantization

Particle 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 information

Notes on Black body spectrum

Notes on Black body spectrum Notes on Black body spectrum Stefano Atzeni October 9, 216 1 The black body Radiation incident on a body can be absorbed, reflected, transmitted. We call black body an ideal body that absorbs all incident

More information

Chemistry 431. Lecture 1. Introduction Statistical Averaging Electromagnetic Spectrum Black body Radiation. NC State University

Chemistry 431. Lecture 1. Introduction Statistical Averaging Electromagnetic Spectrum Black body Radiation. NC State University Chemistry 431 Lecture 1 Introduction Statistical Averaging Electromagnetic Spectrum Black body Radiation NC State University Overview Quantum Mechanics Failure of classical physics Wave equation Rotational,

More information

3. Photons and phonons

3. Photons and phonons Statistical and Low Temperature Physics (PHYS393) 3. Photons and phonons Kai Hock 2010-2011 University of Liverpool Contents 3.1 Phonons 3.2 Photons 3.3 Exercises Photons and phonons 1 3.1 Phonons Photons

More information

Today. Spectra. Thermal Radiation. Wien s Law. Stefan-Boltzmann Law. Kirchoff s Laws. Emission and Absorption. Spectra & Composition

Today. Spectra. Thermal Radiation. Wien s Law. Stefan-Boltzmann Law. Kirchoff s Laws. Emission and Absorption. Spectra & Composition Today Spectra Thermal Radiation Wien s Law Stefan-Boltzmann Law Kirchoff s Laws Emission and Absorption Spectra & Composition Spectrum Originally, the range of colors obtained by passing sunlight through

More information

LIGHT. 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. 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 information

Chapter 1. From Classical to Quantum Mechanics

Chapter 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 information

Chapter 13. Phys 322 Lecture 34. Modern optics

Chapter 13. Phys 322 Lecture 34. Modern optics Chapter 13 Phys 3 Lecture 34 Modern optics Blackbodies and Lasers* Blackbodies Stimulated Emission Gain and Inversion The Laser Four-level System Threshold Some lasers Pump Fast decay Laser Fast decay

More information

Thermal Radiation of Blackbodies Lab Partner 1 & Lab Partner 2 12 May 2011

Thermal Radiation of Blackbodies Lab Partner 1 & Lab Partner 2 12 May 2011 Thermal Radiation of Blackbodies Lab Partner 1 & Lab Partner 2 12 May 2011 We report on experiments investigating the thermal radiation from a blackbody. By finding the electromagnetic spectra emitted

More information

The greenhouse effect

The greenhouse effect 16 Waves of amplitude of 1 m roll onto a beach at a rate of one every 12 s. If the wavelength of the waves is 120 m, calculate (a) the velocity of the waves (b) how much power there is per metre along

More information

Stellar Astrophysics: The Continuous Spectrum of Light

Stellar 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 information

Modern Physics. Unit 6: Hydrogen Atom - Radiation Lecture 6.5: Optical Absorption. Ron Reifenberger Professor of Physics Purdue University

Modern Physics. Unit 6: Hydrogen Atom - Radiation Lecture 6.5: Optical Absorption. Ron Reifenberger Professor of Physics Purdue University Modern Physics Unit 6: Hydrogen tom - Radiation Lecture 6.5: Optical bsorption Ron Reifenberger Professor of Physics Purdue University 1 We now have a simple quantum model for how light is emitted. How

More information

Preview. Atomic Physics Section 1. Section 1 Quantization of Energy. Section 2 Models of the Atom. Section 3 Quantum Mechanics

Preview. 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 information

QUANTUM MECHANICS AND MOLECULAR SPECTROSCOPY

QUANTUM MECHANICS AND MOLECULAR SPECTROSCOPY QUANTUM MECHANICS AND MOLECULAR SPECTROSCOPY CHEM 330 B. O. Owaga Classical physics Classical physics is based on three assumptions i. Predicts precise trajectory for particles with precisely specified

More information

CHAPTER 3 The Experimental Basis of Quantum Theory

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 information

Problems with Classical Physics. Blackbody Radiation Photoelectric Effect Compton Effect Bohr Model of Atom

Problems 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 information

Lecture 12. Measurements in Astronomy. Using Light. ASTR 111 Section 002. In astronomy, we need to make remote and indirect measurements

Lecture 12. Measurements in Astronomy. Using Light. ASTR 111 Section 002. In astronomy, we need to make remote and indirect measurements Lecture 12 ASTR 111 Section 002 Measurements in Astronomy In astronomy, we need to make remote and indirect measurements Think of an example of a remote and indirect measurement from everyday life Using

More information

8.5 GREENHOUSE EFFECT 8.6 GLOBAL WARMING HW/Study Packet

8.5 GREENHOUSE EFFECT 8.6 GLOBAL WARMING HW/Study Packet 8.5 GREENHOUSE EFFECT 8.6 GLOBAL WARMING HW/Study Packet Required: READ Tsokos, pp 434-450 Hamper pp 294-307 SL/HL Supplemental: none REMEMBER TO. Work through all of the example problems in the texts

More information

ASTR-1010: Astronomy I Course Notes Section IV

ASTR-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 information

Lecture #8. Light-matter interaction. Kirchoff s laws

Lecture #8. Light-matter interaction. Kirchoff s laws 1 Lecture #8 Light-matter interaction Kirchoff s laws 2 Line emission/absorption Atoms: release and absorb photons with a predefined set of energies (discrete). The number of protons determine the chemical

More information

Experimental Basis for QM Ch3

Experimental 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 information

STSF2223 Quantum Mechanics I

STSF2223 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 information

If light travels past a system faster than the time scale for which the system evolves then t I ν = 0 and we have then

If light travels past a system faster than the time scale for which the system evolves then t I ν = 0 and we have then 6 LECTURE 2 Equation of Radiative Transfer Condition that I ν is constant along rays means that di ν /dt = 0 = t I ν + ck I ν, (29) where ck = di ν /ds is the ray-path derivative. This is equation is the

More information

Physics 1C. Chapter 28 !!!!

Physics 1C. Chapter 28 !!!! Physics 1C Chapter 28!!!! "Splitting the atom is like trying to shoot a gnat in the Albert Hall at night and using ten million rounds of ammunition on the off chance of getting it. That should convince

More information

Physics: Quanta to Quarks Option (99.95 ATAR)

Physics: Quanta to Quarks Option (99.95 ATAR) HSC Physics Year 2016 Mark 95.00 Pages 22 Published Jan 15, 2017 Physics: Quanta to Quarks Option (99.95 ATAR) By Edward (99.95 ATAR) Powered by TCPDF (www.tcpdf.org) Your notes author, Edward. Edward

More information

Planck s Hypothesis of Blackbody

Planck s Hypothesis of Blackbody Course : Bsc Applied Physical Science (Computer Science) Year Ist (Sem IInd) Paper title : Thermal Physics Paper No : 6 Lecture no. 20. Planck s Hypothesis of Blackbody FAQs Q1. What were the shortcomings

More information

1. Historical perspective

1. 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 information

Earth: the Goldilocks Planet

Earth: the Goldilocks Planet Earth: the Goldilocks Planet Not too hot (460 C) Fig. 3-1 Not too cold (-55 C) Wave properties: Wavelength, velocity, and? Fig. 3-2 Reviewing units: Wavelength = distance (meters or nanometers, etc.) Velocity

More information

B. Sc. Physics (H.R.K) Chapter 49: Light and Quantum Physics LIGHT AND QUANTUM PHYSICS

B. 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 information

Classical and Planck picture. Planck s constant. Question. Quantum explanation for the Wein Effect.

Classical and Planck picture. Planck s constant. Question. Quantum explanation for the Wein Effect. 6.1 Quantum Physics. Particle Nature of Light Particle nature of Light Blackbody Radiation Photoelectric Effect Properties of photons Ionizing radiation Radiation damage x-rays Compton effect X-ray diffraction

More information

THREE MAIN LIGHT MATTER INTERRACTION

THREE MAIN LIGHT MATTER INTERRACTION Chapters: 3and 4 THREE MAIN LIGHT MATTER INTERRACTION Absorption: converts radiative energy into internal energy Emission: converts internal energy into radiative energy Scattering; Radiative energy is

More information

Chapter 7: Quantum Statistics

Chapter 7: Quantum Statistics Part II: Applications SDSMT, Physics 2013 Fall 1 Introduction Photons, E.M. Radiation 2 Blackbody Radiation The Ultraviolet Catastrophe 3 Thermal Quantities of Photon System Total Energy Entropy 4 Radiation

More information

AST 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] 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 information

Semiconductor Physics and Devices

Semiconductor 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 information

Chapter 39. Particles Behaving as Waves

Chapter 39. Particles Behaving as Waves Chapter 39 Particles Behaving as Waves 39.1 Electron Waves Light has a dual nature. Light exhibits both wave and particle characteristics. Louis de Broglie postulated in 1924 that if nature is symmetric,

More information

EVOLUTION OF STARS HERTZSPRUNG-RUSSELL DIAGRAM

EVOLUTION OF STARS HERTZSPRUNG-RUSSELL DIAGRAM VISUAL PHYSICS ONLINE EVOLUTION OF STARS HERTZSPRUNG-RUSSELL DIAGRAM The total power radiated by a star is called its intrinsic luminosity L (luminosity). The apparent brightness (apparent luminosity)

More information

MASSACHUSETTS INSTITUTE OF TECHNOLOGY Department of Physics Problem Solving 10: The Greenhouse Effect. Section Table and Group

MASSACHUSETTS INSTITUTE OF TECHNOLOGY Department of Physics Problem Solving 10: The Greenhouse Effect. Section Table and Group MASSACHUSETTS INSTITUTE OF TECHNOLOGY Department of Physics 8.02 Problem Solving 10: The Greenhouse Effect Section Table and Group Names Hand in one copy per group at the end of the Friday Problem Solving

More information

CHAPTER 3 The Experimental Basis of Quantum

CHAPTER 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 information

Minimum Bias Events at ATLAS

Minimum Bias Events at ATLAS Camille Bélanger-Champagne Lehman McGill College University City University of New York Thermodynamics Charged Particle and Correlations Statistical Mechanics in Minimum Bias Events at ATLAS Statistical

More information

aka Light Properties of Light are simultaneously

aka Light Properties of Light are simultaneously Today Interaction of Light with Matter Thermal Radiation Kirchhoff s Laws aka Light Properties of Light are simultaneously wave-like AND particle-like Sometimes it behaves like ripples on a pond (waves).

More information

Physics Lecture 6

Physics 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 information

INTRODUCTION Radiation differs from conduction and convection in that it does not require the presence of a material medium to take place.

INTRODUCTION Radiation differs from conduction and convection in that it does not require the presence of a material medium to take place. RADIATION INTRODUCTION Radiation differs from conduction and convection in that it does not require the presence of a material medium to take place. Radiation: The energy emitted by matter in the form

More information

Chapter 30 Quantum Physics 30.1 Blackbody Radiation and Planck s Hypothesis of Quantum Energy 30.2 Photons and the Photoelectric Effect 30.

Chapter 30 Quantum Physics 30.1 Blackbody Radiation and Planck s Hypothesis of Quantum Energy 30.2 Photons and the Photoelectric Effect 30. Chapter 30 Quantum Physics 30.1 Blackbody Radiation and Planck s Hypothesis of Quantum Energy 30.2 Photons and the Photoelectric Effect 30.3 The Mass and Momentum of a Photon 30.4 Photon Scattering and

More information

General Physics (PHY 2140)

General 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 information

Chapter 27. Quantum Physics

Chapter 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 information

CHAPTER NUMBER 7: Quantum Theory: Introduction and Principles

CHAPTER NUMBER 7: Quantum Theory: Introduction and Principles CHAPTER NUMBER 7: Quantum Theory: Introduction and Principles Art PowerPoints Peter Atkins & Julio De Paula 2010 1 mm 1000 m 100 m 10 m 1000 nm 100 nm 10 nm 1 nm 10 Å 1 Å Quantum phenomena 7.1 Energy quantization

More information

Phys 322 Lecture 34. Chapter 13. Modern optics. Note: 10 points will be given for attendance today and for the rest of the semester.

Phys 322 Lecture 34. Chapter 13. Modern optics. Note: 10 points will be given for attendance today and for the rest of the semester. Chapter 13 Phys 322 Lecture 34 Modern optics Note: 10 points will be given for attendance today and for the rest of the semester. Presentation schedule Name Topic Date Alip, Abylaikhan lasers Nov. 30th

More information

Chapter 11 FUNDAMENTALS OF THERMAL RADIATION

Chapter 11 FUNDAMENTALS OF THERMAL RADIATION Chapter Chapter Fundamentals of Thermal Radiation FUNDAMENTALS OF THERMAL RADIATION Electromagnetic and Thermal Radiation -C Electromagnetic waves are caused by accelerated charges or changing electric

More information

With certain caveats (described later) an object absorbs as effectively as it emits

With certain caveats (described later) an object absorbs as effectively as it emits Figure 1: A blackbody defined by a cavity where emission and absorption are in equilibrium so as to maintain a constant temperature Blackbody radiation The basic principles of thermal emission are as follows:

More information

CHAPTER 27 Quantum Physics

CHAPTER 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 information

The ELECTRON: Wave Particle Duality. chapter 4

The ELECTRON: Wave Particle Duality. chapter 4 The ELECTRON: Wave Particle Duality chapter 4 What do we know about light? Before 1900 s scientists thought light behaved as a wave. This belief changed when it was discovered that light also has particle

More information

ATOMIC PHYSICS. history/cosmology/tools/ tools-spectroscopy.htm CHAPTER 9 - FROM SPECTROSCOPY TO ATOMS

ATOMIC PHYSICS.   history/cosmology/tools/ tools-spectroscopy.htm CHAPTER 9 - FROM SPECTROSCOPY TO ATOMS ATOMIC PHYSICS http://www.aip.org/ history/cosmology/tools/ tools-spectroscopy.htm CHAPTER 9 - FROM SPECTROSCOPY TO ATOMS What We Will Study Basics of electromagnetic radiation - The AC generator, again

More information

The Bohr Model of the Atom

The Bohr Model of the Atom Unit 4: The Bohr Model of the Atom Properties of light Before the 1900 s, light was thought to behave only as a wave. Light is a type of electromagnetic radiation - a form of energy that exhibits wave

More information

Radiation Processes. Black Body Radiation. Heino Falcke Radboud Universiteit Nijmegen. Contents:

Radiation Processes. Black Body Radiation. Heino Falcke Radboud Universiteit Nijmegen. Contents: Radiation Processes Black Body Radiation Heino Falcke Radboud Universiteit Nijmegen Contents: Planck Spectrum Kirchoff & Stefan-Boltzmann Rayleigh-Jeans & Wien Einstein Coefficients Literature: Based heavily

More information

Take away concepts. What is Energy? Solar Radiation Emission and Absorption. Energy: The ability to do work

Take away concepts. What is Energy? Solar Radiation Emission and Absorption. Energy: The ability to do work Solar Radiation Emission and Absorption Take away concepts 1. 2. 3. 4. 5. 6. Conservation of energy. Black body radiation principle Emission wavelength and temperature (Wien s Law). Radiation vs. distance

More information

Class 21. Early Quantum Mechanics and the Wave Nature of Matter. Physics 106. Winter Press CTRL-L to view as a slide show. Class 21.

Class 21. Early Quantum Mechanics and the Wave Nature of Matter. Physics 106. Winter Press CTRL-L to view as a slide show. Class 21. Early and the Wave Nature of Matter Winter 2018 Press CTRL-L to view as a slide show. Last Time Last time we discussed: Optical systems Midterm 2 Today we will discuss: Quick of X-ray diffraction Compton

More information

Mechanisms of heat transfer

Mechanisms of heat transfer Lecture 4 Mechanisms of heat transfer Pre-reading: 17.7 Review Heat can be transferred from one object to another due to a temperature difference. The properties of many objects change with temperature:

More information

Problem Set 2 Solutions

Problem Set 2 Solutions Problem Set 2 Solutions Problem 1: A A hot blackbody will emit more photons per unit time per unit surface area than a cold blackbody. It does not, however, necessarily need to have a higher luminosity,

More information

Electromagnetic spectrum Electromagnetic radiation

Electromagnetic spectrum Electromagnetic radiation Chapter 4 Section 1 Electromagnetic spectrum includes all the different wave lengths of radiation. Electromagnetic radiation is a form of energy that exhibits wave like behavior as it travels through space.

More information