Pleasebe

Seated

Physics is PhunNovember 2005

Einstein

and the

2005 Year of Physics

In 1905, at the age of 25,Einstein published papers

on Brownian Motion, the Photoelectric Effect,

and Relativity.

This achievementhas been called

the most productive yearfor any scientist,

ever.

The centennialof this event

is celebrated as the2005 Year of Physics

Quote of the Century:

"The word ‘genius’ isn'tapplicable in football. A geniusis a guy like Norman Einstein."

--Joe Theismann, NFL footballquarterback & sports analyst.

In the matter of physics, the first lessons should contain nothing but

what is experimental and interesting to see. A pretty experiment is in itself often more valuable than

twenty formulae extracted from our minds.

 

-Albert Einstein

Some Reference materials:National Science Foundation web site

American Association of Physics Teachers web site

University of Maryland Physics Question of the Week web site

Topics for this evening:1.Brownian Motion2.The Photoelectric

Effect3.Relativity

Brownian motion:is the small molecularmotion inherent in allmolecules, even at thelowest possibletemperature.

Discovered by botanistRobert Browne (1773-1858)“..in 1827. The story goes that Brown was studying

pollen particles floating in water under the microscope.”

From Wikipedia, the free encyclopedia.

Brownian Motionof

smoke particlesdemonstration

Java appletofBrownian motion

Mechanical Modelof

Brownian Motion

“More accurate”description:

statistical fluctuationsrequiring ~10,000 netmolecular collisions tochange particle motion.

Implications ofBrownian Motion:

1. Air pressure2. Diffusion of gases

Reducing Brownian MotionMinimizing molecularmotion in atomic clocksincreases accuracy ofclocks and GPS.

William PhillipsProfessor of Physics,University of Maryland

Nobel prize in 1997 forLaser cooling of atoms

Video showing magneticallytrapped block of cesium atoms

ThePhotoelectric Effect:

describes the particle behavior of light.

Einstein received the 1921 Nobel Prize in Physics

for work on thePhotoelectric Effect

Ef = h f

E = photon energyh = Planck’s constant

(~6.6x10-34 Joule-sec)f = light frequency

KEe = Ef – W = hf - W

A single photon of light is absorbed byan electron, causing it to be ejectedfrom the surface of the metal.

Graphic from Wikipedia, the free encyclopedia.

Demonstrations

1. Photoelectric effect in zinc

2. Full photoelectric effect

Applications:

Solar powerSolar enginesSolar switches“Hydrogen” economy

2005 Nobel prizein Physics to

Glauber, Hall, & Haensch(application of quantum

nature of light to build atomic clocks to 10-15 accuracy and

thus improve GPS accuracy )

Relativity:

deals in part withframes of referenceand how we viewphysical phenomena.

Physics experiments arefully accurate only in aninertial frame of referenceor in a local inertial frame.

When might a physicsexperiment be correct?

Galilean Relativityand theFunnel Cart Demonstration

Local inertialframe of referencedemonstration

Einstein’sfavorite demonstration

The Speed of Lightand the search for aPreferred Inertial

Frame of Reference

TheMichelson-Morleyexperiment

1. There is NOpreferredframe of

reference.

2. Thespeed of Light

is the same in allinertial frames

Applicationsof Relativity

Michelson Interferometerwith White Light

Color Mixing:W = R + G + B

W – R = G + B = CW – G = R + B = MW – B = R + G = Y

MichelsonInterferometersetup usingWhite Light

Michelson InterferometerwithWhite Light

Michelson Interferometerwith

White Light

Full motion of mirrorfor this video

~10 μ = 0.000,010m = 0.01 mm

We are on the web at

http://www.physics.umd.edu/lecdem/

Animated Gifs compliments of bellsnwhistles.com

The EndSee you in January!