Transcript EM Lecture Slides

Light etc.
PHY 2054 Spring 2011
April 13, 2011
• Today we start the study of
electromagnetic waves and LIGHT as in
“let there be”.
• This will lead to a discussion of
– Polarization
– Mirrors
– Lenses
– Perhaps interference and diffraction
• There are available experiments for
each of these. Not sure how far we will
get but we will get there quickly!
April 2011 Time is on the move!
Sunday
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
1
2
3
4 Complete
Induction
5
6
AC
7
8
AC
Quiz?
9
10
11
COMPLETE
AC EXPT
12
13 OPTICS
14
15 OPTICS
16
17
18
EXAM #3
(No Optics)
19
20 OPTICS
21
22 OPTICS
23
24
25 (LAST LASS)
OPTICS
26
27
28
29
30 FINAL
HPA 119
9:00 AM
EM Waves
POLARIZATION
Quiz
WHERE
IS
THE
FINAL
EXAM??
What’s on Exam #3?

Questions!
5
Multiple choice questions
Three problems covering
Magnetism
Induction
AC
Circuits
A sound wave
A.
B.
C.
D.
is a transverse wave
is a longitudinal wave
travels at the speed of
light
has a color spectrum
Sound Waves
Light





James Clerk Maxwell (1831 - 1879) was a genius who
studied the properties of Electricity and Magnetism. He
took a mathematical approach. He published his first
scientific paper when he was 15 years old.
The four mathematical equations Maxwell produced are
ranked with Sir Isaac Newton's laws of motion and
Albert Einstein's theory of relativity as the most
fundamental contributions to (“classical” )physics.
Maxwell’s equations predicted that the electric field and
the magnetic field could propagate through empty space.
The calculated velocity of these waves turned out to
match the speed of light to a very close precision.
It was later demonstrated that these waves were, in fact,
light waves.
Maxwell’s Equations
Gauss’s Law
No Mag Poles!!
 

d 
Faraday’s Law
Ampere’s Law
Displacement
Current
Which way is the electric field at P pointing?
A
B
C
D
E
P
Left
Right
Up
Down
In/Out
Electromagnetic Wave Generation
There is also a current here so there is
one of those B things.
Both Together
Propagation


The electric and magnetic fields are predicted (and verified)
to be perpendicular to each other.
The propagation velocity is found to be “c”, the speed of
light in a vacuum.


of Light
c=3x108 m/sec.
Maxwell calculated that the speed of light in a vacuum to be
c
1
 0 0
Propagation
of Light
l
c

1
 0 0
Since the E and B fields (vectors) are perpendicular to the
direction of propagation, the wave is said to be
TANSVERSE.

Because of this fact, the light wave can be “polarized”

The wavelength l of the wave is shown in the diagram.

The product of the frequency and the wavelength is c so we
see that light can come in different wavelengths (c is a
constant)
Waving Along
Sir Isaac
The Electromagnetic Spectrum
Polarization
Polarization
Polarized
Unpolarized
Changing It Around
Crossed Polarizer's can Transmit light!
Big Money!
Today’s Experiment
Polarized Light
 Read the material at the
beginning of the experiment
that we haven’t covered

 Don’t
read what we covered
today
Do the experiment
 Next time the math!

Get a Blue Box and get to work!!!
OPTICS
STUFF