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PHYS 342 Modern Physics Project Discussion I

Basic Requirements of Projects 

Grading Method Quality of Slides

Quality of Physics

Presentation Skills 

Presentation(Points given by your classmates)

10 20 20

Quality of Writing

Quality of Physics

Broadness of Contents

Report (Points given by me)

10 20 10

Attendance of Presentation  (decided by your evaluation)

10

TOTAL 100

Basic Requirements of Projects 

To get good credits for your report,  the report should have at least 20,000 characters, which is roughly 5 pages of letter size paper. The due time of the report is the time you give the presentation.  There is no extension.

Each presentation is 20 minutes (15 minutes talk plus 5 minutes questions). There is no extension time or make‐up time. Without reserving a time slot and giving a talk,  the presentation credit is zero.

The policy to choose the project topic:  1) you can choose any one of the topics from my project lists in “project discussion I, II, III”.  However, any topic can only be chosen by one team. “first come first serve” .  The group that emails the team member and title information to leluo@iupui.edu earlier  will get the topic.2) you can choose your own topic. However, you need to present the basic idea of your topic in “project discussion I, II, III”,  and get approval  from me.3) In any case, you need to email your team member and title information to leluo@iupui.edu before Apr.15 to secure a  presentation time slot.4) The maximum number of  people for each team is three.

Projects for Discussion

Today's Projects for Discussion:

a) Modern Physics ‐‐ Modern Physics Researches at IUPUIb) Modern Experiments for Testing Special Relativityc) Quantization of thermal radiation: Blackbody Radiationd) Quantization of gravity: Gravitational Wave, Gravitions and the LIGO Projecte) Project selected by you! 

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Modern Physics Researches at IUPUI

Projects:  You need to interview at least one of the faculty in each of the five category to get knowledge of their research.  Based on these interviews, you write a report about modern physics researches at IUPUI from your own perspective of view.

Faculty in the physics department at IUPUI conduct theoretical and experimental investigations in many areas of modern physics, such as biophysics, atomic, molecular and optical physics, condensed matter/materials physics,the fundamental forces of nature, and physics education.

http://physics.iupui.edu/research

Modern Physics Researches at IUPUI

Atomic, Molecular and Optical PhysicsLe LuoZhe‐Yu Jeff OuGautam VemuriTony Lee

Biological PhysicsMarvin D. KempleHoria PetracheSteve PresséStephen WassallFangqiang Zhu

Condensed Matter PhysicsRuihua ChengRicardo DeccaYogesh N Joglekar

Physics EducationAndrew Gavrin

Note: We have five areas of research. For AMO physics, you need to choose other faculty instead of me for interview! ( I will have a lab tour for the whole class later on)

Projects for Discussion

Today's Projects for Discussion:

a) Modern Physics ‐‐ Modern Physics Researches at IUPUIb) Modern Experiments for Testing Special Relativityc) Quantization of thermal radiation: Blackbody Radiationd) Quantization of gravity: Gravitational Wave, Gravitions and the LIGO Projecte) Project selected by you! 

Modern Experiments for Testing Special Relativity

Projects:  You can make an investigation of modern experiments of testing special relativity, and choose 2~3 experiments to write a review.  Here I require you to investigate experiments implemented after 1980s (including 1980s),  which are more precise experiments including modern technologies.

Some experiments are listed below.

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Modern Experiments to Test Special Relativity

Early experiments (pre-1905): Round-trip tests of light speed isotropy: Michelson and Morley, Kennedy and Thorndike.

Experiments (after 1905): One-way tests of light speed isotropy: Cialdea, Krisher, Champeny,

Turner & Hill.Tests of light speed from moving sources: Cosmological sources by

DeSitter and Brecher; Terrestrial sources by Alvaeger and Sadeh.Measurements of the speed of light and other limits on it: NBS

measurements, 1983 Redefinition of the meter, Limits on variations with frequency, Limits on photon mass.

Tests of the principle of relativity and Lorentz invariance: Trouton and Noble.

Tests of the isotropy of space: Hughes-Drever, Prestage, Lamoreaux, Chupp, Phillips, Brillet and Hall.

Modern Experiments to Test Special Relativity

Tests of time dilation and transverse Doppler effect: Ives and Stilwell, Particle lifetimes, Doppler shift measurements.

Tests of the twin paradox: Haefle and Keating, Vessot et al, Alley, Bailey et al., The clock hypothesis.

Tests of relativistic kinematics: Elastic scattering, Limits of velocity c, Relativistic mass Variations, Calorimetric test of SR.

Other experiments: Fizeau, Sagnac, Michelson and Gale, g-2 tests of SR, The global positioning system (GPS), Lunar laser ranging, Cosmic background radiation (CMBR), Constancy of physical constants…

An excellent source of information on experimental tests of Special Relativity is the webpage:

http://math.ucr.edu/home/baez/physics/Relativity/SR/experiments.html

SR makes many predictions, which are well tested:– Isotropy of the speed of light – 42– Isotropy of space – 8– Constancy of the speed of light – 12– Time dilation and Doppler – 16– Length contraction – ZERO– Twin paradox – 5– Relativistic kinematics – 23– Relativistic velocity addition – 5– Variation of c with frequency – 4– Other – 14

Overview: Experimental Tests of SR Michelson – Morley Experiment (1887)Michelson – Morley Experiment (1887)

• Finicky experiment: ±0.002 °C, mechanical stability ~nm/m• Result: upper limit of 7.5 km/s (earth relative to aether)

*Light Source

Mirror

Mirror

BeamSplitter

Observer

Telescope

Michelson and Morley, Am. J. Sci. 34, 333 (1887).

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Brillet and Hall Experiment (1979)Brillet and Hall Experiment (1979)

• Vastly less finicky than Michelson-Morley– Invar components with low thermal expansion– Rotating Fabry-Perot etalon is vacuum– Uses frequency (motion 1 wavelength/sec => 1 Hz, ~1 part in 1015)

• Result: ∆f/f = (1.5±2.5) ·10-15 => Vearth < 0.02 km/s

Single-Mode Laser HeterodyneFrequency

Counter

Single-ModeLaser

High-FinesseFabry-Perot

Rotating TableBrillet and Hall,

Phys. Rev. Lett. 42, 549 (1979)

Speed of Light Emitted by Moving SourcesSpeed of Light Emitted by Moving Sources

As a simple test theory, assume the observed speed oflight is given by

Vobs = c + k Vsourcewith k to be determined by experiment.

1) A test at CERN using π0 decay:k < 4·10-4

2) Distant supernovas have a velocity spread of the remnants ~10,000 km/s (obtained via Doppler broadening). Observations of supernovas ~5 billion light years away show the light reaches us within ~10 days:

k < 10-9

Particle Experiment Tests of SRParticle Experiment Tests of SR

• Today particle physicists test SR.

– Electron kinetic energy as a function of speed agrees with the prediction of SR to within ~1% (1939)

– The Lorentz limiting speed is equal to the speed of light to within 12 parts per million (1972-1991).

– Super Kamiokande neutrino oscillation observations put a limit of 10-24 on the speed difference between νμand ντ.

Elastic Proton-Proton ScatteringElastic Proton-Proton Scattering

Akerlof et al, Phys. Rev. 159, 1138 (1967).

Newtonian mechanics predicts inthe lab frame the scattered

particles will have an angle of 90°.

This experiment verified the kinematics of elastic scattering to about ½%,for incident protons from 5 to 13.4 GeV/c (v/c=0.98 - 0.998).

For high-energy protons that is manifestly not so:

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Time Dilation in 7Li+ Ion Storage RingTime Dilation in 7Li+ Ion Storage RingElectron-cooledIon Storage Ring

v/c = 0.064

Fixed laserDetectors

Tunable laser

MirrorHalf-silvered

Mirrors

Freq. Monitor

• Fixed laser is locked to a double resonance of the 7Li+ ions with its parallel and anti-parallel laser beams.

• Parallel alignment of beams to 70 μrad.• 7Li+ linewidth is large, so the fixed laser saturates the

resonance and the tunable laser scans it to achieve resolution comparable to the laser linewidths

• Measurement/SR = 0.9999999995 ± 0.0000000018Saathoff et al, Phys. Rev. Lett. 91, 190403 (2003).

Time Dilation in atomic clockTime Dilation in atomic clock

https://www.youtube.com/watch?v=gdRmCqylsME

Visibly Superluminal Astronomical SourcesVisibly Superluminal Astronomical Sources• There are numerous astronomical objects observed to

have visible speeds greater than c.

• In 1994 GRS 1915+105 was observed to emit material about the mass of the moon, with an apparent speed of 1.25 c (distance times angular speed). The uncertainty in its distance (40,000 ly) is much less than 25%.

Projects for Discussion

Today's Projects for Discussion:

a) Modern Physics -- Modern Physics Researches at IUPUIb) Modern Experiments for Testing Special Relativityc) Quantization of thermal radiation: Blackbody Radiationd) Quantization of gravity: Gravitational Wave, Gravitions and the LIGO Projecte) Project selected by you!

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Blackbody Radiation

Projects: You make a research and write a review to include three contents.

(a) The experimental phenomena of blackbody radiation.(b) The Planck theory to explain the experimental observation.(c) The application of blackbody radiation in modern science and technology.

BLACK BODY RADIATIONBLACK BODY RADIATION

• Object that is HOT (anything > 0 K is considered “hot”) emits EM radiation

• For example, an incandescent lamp is red HOT because it emits a lot of infrared waves

Photo with an IR cameraPhoto with an IR camera IR CatIR Cat

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IR houseIR house Spectroscopic studiesSpectroscopic studies

“Room temperature” radiation“Room temperature” radiation

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Blackbody Approximation

• A good approximation of a black body is a small hole leading to the inside of a hollow object

• The HOLE acts as a perfect absorber

• The Black Body is the HOLE

Black-Body Radation Laws:

1- The Rayleigh-Jeans Law (classical theory)2- The Planck Law (quantum theory)3- The Wien Displacement Law (observation)4- The Stefan-Boltzmann Law (observation)

Blackbody radiation with classical EM theory and statistical physics

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Black-Body Radiation LawsBlack-Body Radiation Laws

1 The Rayleigh-Jeans Law.* It agrees with experimental

measurements for long wavelengths.

* It predicts an energy output that diverges towards infinity as wavelengths grow smaller.

* The failure has become known as the ultraviolet catastrophe.

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2),( ckTTI

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Ultraviolet catastropheUltraviolet catastrophe

2 Planck Law

Black-Body Radiation LawsBlack-Body Radiation Laws

1

15

22),(

kThc

e

hcTI

How Planck modeled the BBHow Planck modeled the BB

• assumed the cavity radiation came from atomic oscillations in the cavity walls

• made two assumptions about the nature of the oscillators in the cavity walls

Blackbody radiation with classical EM theory and statistical physics

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Planck’s Assumption 1Planck’s Assumption 1

The energy of an oscillator can have only certain discrete values En

– En = nhƒ• n =0,1,2,…; n is called the quantum number• h is Planck’s constant = 6.63 x 10-34 Js• ƒ is the frequency of oscillation

– the energy of the oscillator is quantized

Planck’s Assumption 2Planck’s Assumption 2

The oscillators emit or absorb energy when making a transition from one quantum state to another

– The entire energy difference between the initial and final states in the transition is emitted or absorbed as a single quantum of radiation

– An oscillator emits or absorbs energy only when it changes quantum states

cosmic microwave background

Nobel Prize 1976

CMBR – the most perfect Black Bodym

icro

wav

e

Far i

nfra

red

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The Nobel Prize in Physics 2006

"for their discovery of the blackbody form and anisotropy of the cosmic microwave background radiation"

John C. Mather

George F. Smoot

https://www.youtube.com/watch?v=1kqWWLpyMpY

“Faces of God”

https://www.youtube.com/watch?v=3pu84BQVxK4

Blackbody ApplicationsProjects for Discussion

Today's Projects for Discussion:

a) Modern Physics -- Modern Physics Researches at IUPUIb) Modern Experiments to Test Special Relativityc) Quantization of thermal radiation: Blackbody Radiationd) Quantization of gravity: Gravitational Wave, Gravitons and the LIGO Projecte) Project selected by you!

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Gravitational Wave, Gravitons and the LIGO Project

Projects: You do a study in GW and write a review to include three contents.

(a) Explain what is gravitational wave and graviton.(b) Introduce the LIGO project.(c) The influence of verifying gravitational wave on modern physics.

The Nature of Gravity

Newton• “Action at a distance”.

• Newton’s Law describes effect of gravity but does not explain it.

Einstein• Gravity is spacetime curvature.

• Any mass/energy bends spacetimenear it.

• Freely falling objects follow the local background curvature.

What are Gravitational Waves?• “Ripples in spacetime” – any rapidly moving mass

generates fluctuations in spacetime curvature.

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GW Sources – Binaries GW Sources – Pulsars• Pulsars are rapidly rotating neutron stars..

GW Sources – Bursts• When massive stars reach the end of their lives, they

collapse in a supernova explosion.

Gravitational waves• Underlying field is the gravitational tidal field (g’)

• Oscillations produce gravitational waves in exactly the same manner as electromagnetic waves

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Gravitational waves• Underlying field is the gravitational tidal field (g’)

• Oscillations produce gravitational waves in exactly the same manner as electromagnetic waves

• Strength is given by the strain amplitude (h)

» Typically of order 10 -21 or less!

GW Detection – Interferometers

Several ground based interferometers are now operating or are being built –

• LIGO – US project. Two 4km and one 2km detector.

http://www.ligo.caltech.edu/

https://www.youtube.com/watch?v=RzZgFKoIfQI

Projects for Discussion

Today's Projects for Discussion:

a) Modern Physics -- Modern Physics Researches at IUPUIb) Modern Experiments to Test Special Relativityc) Quantization of thermal radiation: Blackbody Radiationd) Quantization of gravity: Gravitational Wave, Gravitons and the LIGO Projecte) Project selected by you (you needs to present your idea first in the next two dicussion)!