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## ELECtromagnetic waves

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### Title: ELECtromagnetic waves Author: jbindell Last modified by: jbindell Created Date: 4/12/2011 6:31:24 PM Document presentation format: On-screen Show (4:3) – PowerPoint PPT presentation

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Title: ELECtromagnetic waves

1
ELECtromagnetic waves
• Light etc.
• PHY 2054 Spring 2011
• April 13, 2011

2
Title
• 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!

3
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 EM Waves POLARIZATION 14 15 OPTICS Quiz 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 119 900 AM
4
WHERE IS THE FINAL EXAM??
5
Whats on Exam 3?
• Questions!
• 5 Multiple choice questions
• Three problems covering
• Magnetism
• Induction
• AC Circuits

6
A sound wave
1. is a transverse wave
2. is a longitudinal wave
3. travels at the speed of light
4. has a color spectrum

7
Sound Waves
8
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.
• Maxwells 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.

9
Maxwells Equations
Gausss Law
No Mag Poles!!
Amperes Law
Displacement Current
10
Which way is the electric field at P pointing?
A Left B Right C Up D Down E In/Out
? P
11
Electromagnetic Wave Generation
12
There is also a current here so there is one of
those B things.
13
Both Together
14
Propagation of Light
• 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.
• c3x108 m/sec.
• Maxwell calculated that the speed of light in a
vacuum to be

15
Propagation of Light
l
• 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)

16
Waving Along
17
Sir Isaac
18
The Electromagnetic Spectrum
19
Polarization
20
Polarization
Polarized Unpolarized
21
Changing It Around
22
Crossed Polarizer's can Transmit light!
23
Big Money!
24
Todays Experiment
• Polarized Light
• Read the material at the beginning of the
experiment that we havent covered
• Dont read what we covered today
• Do the experiment
• Next time the math!

25
Get a Blue Box and get to work!!!

OPTICS STUFF