Welcome to PHYS 201Modern Physics

Fall 2017

Meeting times:MWF 10:00-10:50am; F 2:00-2:50pm

Co-requisite PHYS 251Experimental Atomic Physics

Textbook

Required text:Modern Physics by R. A. Serway, C. J. Moses, C. A. Moyer,

Possibly useful math resource:M. L. Boas, Mathematical Methods in the Physical Sciences, 3rd Ed.

Necessary background

Prerequisites: This course assumes a solid background in first year physics and math.- Full year of calculus-based general physics PHYS

101-102. Algebra-based general physics courses PHYS 107-108 are less optimal . AP Physics is not usually sufficient.

- Full year of calculus at the level of Math 111-112 (and here AP credit is sufficient).

This is a fast-passed and challenging course. Judge your preparedness before you dive in!

Grading

Past years grade assignment

25%30%

20% 20%

A 92 B- 74

A- 87 C+ 69

B+ 84 C 64

B 79 C- 59

This assignment

is likely to be adjusted

for the test scores.

There will be extra credit opportunities!

Homeworks

12 assignments, due beginning of the corresponding Friday class.

Late assignments will be accepted with a 50% penalty when submitted on or before Monday class following the due date.

Any assignment turned in after that time will not be accepted (unless you obtained a permission form me beforehand).

http://www.physics.wm.edu/~inovikova/phys201/CourseSchedule.htm

Homeworks

Comments/responses :“Modern Physics” is a COLL200course, reaching out into CSI(Cultures, Societies, and Individuals).There will be weekly readingassignments regarding the historicalsignificance of the events discussedin class.After each discussion, you shouldread these essays and write roughly½ page of thoughts, comments, andquestions about the material.

http://www.physics.wm.edu/~inovikova/phys201/CourseSchedule.htm

My contact information

Office : Small 251E-mail : ixnovi[at]wm.edu or inovikova[at]physics.wm.eduOffice hours : Wednesday 11am – 12pm; Thursday 1-2pmWeb-site : http://physics.wm.edu/~inovikova/phys201/phys201.htm or in Blackboard

Area of research: experimental atomic physics and quantum opticsResearch projects: quantum memory and slow light, miniature atomic clocks, “squeezed” light, optical microresonators, optical properties of thin films, etc.Lab location: Small 65, 34 (basement)Web-site: http://physics.wm.edu/~inovikova/group.html

Questions? Requests? Opinions?

And now back to physics!

Birth year of modern physics - 1895

Telephones

Automobiles

Industry (steam engine-driven)Electricity

And now back to physics!

The more important fundamental laws and facts of physical science have all been discovered that the possibility of their ever being supplanted in consequence of new discoveries is exceedingly remote… Our future discoveries must be looked for in the sixths place of decimals.

There is nothing new to be discovered in physics now. All that remains is more and more precise measurements.

Lord Kelvin, 1900

A. A. Michelson, 1900

“Classical” physics – XIX century

√ Mechanics

√ Electromagnetism

√ Thermodynamics

√ Optics

Log (size)

Spe

ed

0

c

19th-century physics

Gen

eral

rel

ativ

ity

Qua

ntum

mec

hani

cs Special relativity

“Classical” physics – XIX century

XX century – “Modern” physics√ Special and general relativity

√ Quantum mechanics

√Atomic and molecular physics

√ Nuclear and particle physics

√ Mechanics

√ Electromagnetism

√ Thermodynamics

√ Optics

“Classical” physics: Conservation laws

• Conservation of energy : The sum of energy (in all its forms) is conserved (does not change) in all interactions.

• Conservation of linear momentum : In the absence of external forces, linear momentum is conserved in all interactions.

• Conservation of angular momentum : In the absence of external torque, angular momentum is conserved in all interactions.

• Conservation of charge : Electric charge is conserved in all interactions.

“Classical” physics: Mechanics

Newton’s first law:

An object in motion with a constant velocity will continue in motion unless acted upon in some net external force.

Newton’s second law:

Newton’s third law:

( )dt

vmdamF

rrr

==

2112 FFrr

−=

“Classical” physics: Mechanics

Galilean transformation:

Relates the time and space coordinates between two inertial systems in relative motion.

“Classical” physics: Mechanics

Galilean transformation:

Relates the time and space coordinates between two inertial systems in relative motion.

“Classical” physics: Electromagnetism

Gauss’s law (electricity)

Gauss’s law (magnetism)

Faraday’s law

Ampere’s law

2

0

10

BE E

t

EB B

c t

∂∂∂∂

∇ ⋅ = ∇× = −

∇ ⋅ = ∇× =

rr r r r

rr r r r

Differential form in vacuum

“Classical” physics: Electromagnetism

22

2 2

10

EE

c t

∂∂

∇ − =r

r

Wave equation solution:

Maxwell’s equations simplify to the wave equation for the electric (and magnetic) fields:

( , ) cos( )E r t t k rω∝ ± ⋅rr r r

/c kω=r

which has a simple sine-wave solution:

“Classical” physics: Wave optics…but what’s waving???

A wave needs a medium to propagate -“ether” or “aether.” Light waves were found to be solutions to Maxwell’s Equations, showing that light is electromagnetic wave, propagating at the speed c:

But in what reference frame?

Another problem with Maxwell equations – their form changes under Galilean transformation!

“Classical” physics: Thermodynamics

First law of thermodynamics:

The change in the internal energy ∆U of a system is equal of the heat Q added ti the system plus the work Wdone on the system.

∆U = Q + W

Second law of thermodynamics :

It is impossible to convert heat completely into work without some other change taking place.

Ideal gas equations:

PV=nkBT

Ultraviolet catastrophe

As an object gets hot, it radiates energy. Black body absorbs and emits radiation on all frequencies. An ideal blackbody radiator can beconsidered as a black box with a tiny hole.

Classical thermodynamics failed to explain the spectrum of the blackbody radiation.

Birth of “modern” physics

In a speech to the Royal Institution in 1900, Lord Kelvin himself described two “dark clouds on the horizon ” of physics:

The question of the existence of an electro-magnetic medium—referred to as “ether” or “aether.”

The failure of classical physics to explain blackbody radiation.

Special relativity

Quantum mechanics

Birth of modern physics (cont)

• Discovery of the X-rays (Roentgen, 1895)• Discovery of Radioactivity (Becquerel, 1896)

• Discovery of the electron (Thomson, 1896)• Discovery of the Zeeman effect - splitting of atomic

spectral lines in magnetic field (Zeeman, 1897)

Nuclear physics

Quantum mechanics, atomic physics

• Special relativity• Basics of quantum mechanics• Introduction to atomic physics and

spectroscopy• Briefly: molecules, solid state physics,

semiconductors, nuclear and particle physics

What we are going to do this semester…

• The effects we are going to discuss are outside of our everyday experiences.

• We have no intuition to guide us!• The correct solution may seem as weird

as any incorrect one.

Why it is challenging?

The recipe of walking through the walls may work for you!

• Keep an eye on the goal. • Believe in yourself.• Pay no attention to the obstacles.

• And be sure to seek help and support when you need it!