Download EM Spectrum

Electromagnetic
Radiation
Physics

Relax and Enjoy the Ride…
It’s quite a ride.
Waves… a review
 Most
waves are either
longitudinal or transverse.
 Sound waves are longitudinal.
 But all electromagnetic waves
are transverse…
?
?
Wave Relationships

Notice from the definitions we can relate the
properties of a wave to one another
frequency  1
period
wavelength
velocity  wavelength  frequency 
period
Wave Relationships

Frequency is usually expressed in the unit of Hertz

This unit is named after a German scientist who studied radio
waves
1
1Hz 
s

For example, if a wave has a period of 10 seconds, the frequency
of the wave would be 1/10 Hz, or 0.1 Hz
Note that light is always traveling at the same speed
(c ~ 3 x 108 m/s)


Remember: velocity = wavelength x frequency


If frequency increases, wavelength decreases
If frequency decreases, wavelength increases
Electromagnetic waves
 Produced
by the movement of
electrically charged particles
 Can travel in a “vacuum” (they do
NOT need a medium
 Travel at the speed of
light
 Also known as EM waves
Wave-particle Duality
 Light
can behave like a wave or like
a particle
 A “particle” of light is called a photon
Radio waves
 Longest
wavelength EM waves
 Uses:





TV broadcasting
AM and FM broadcast radio
Avalanche beacons
Heart rate monitors
Cell phone communication
Microwaves
 Wavelengths
from 1 mm- 1 m
 Uses:





Microwave ovens
Bluetooth headsets
Broadband Wireless Internet
Radar
GPS
Infrared Radiation
 Wavelengths
in between microwaves
and visible light
 Uses:



Night vision goggles
Remote controls
Heat-seeking missiles
Visible light
 Only
type of EM wave able to be
detected by the human eye
 Violet is the highest frequency light
 Red light is the lowest frequency
light
Wavelengths of Light Visible

What we see as white
light is actually made up
of a continuum of
components

Traditionally, we break
white light into red,
orange, yellow, green,
blue, indigo, and violet
(ROY G BIV)

There is actually a
continuous transition of
color, each with its own
wavelength and frequency
Ultraviolet
 Shorter
light
 Uses:




wavelengths than visible
Black lights
Sterilizing medical equipment
Water disinfection
Security images on money
Ultraviolet (cont.)
UVA
UVB and UVC
Energy
Highest of UV
waves
Lower than UVA
Health
risks

Extremely
low risk for
DNA damage
 Can destroy
Vitamin A in
skin

Can cause DNA
damage, leading to
skin cancer
 Responsible for
sunburn
X-rays
 Tiny
wavelength, high
energy waves
 Uses:



Medical imaging
Airport security
Inspecting industrial welds
Gamma Rays
 Smallest
wavelengths, highest
energy EM waves
 Uses



Food irradiation
Cancer treatment
Treating wood flooring
Blackbody Radiation
Cool gas ( ~60K)
Young star ( ~600K)
The Sun (~6000K)
Hot stars in a cluster ( ~60,00
The Sun at Different
Wavelengths
Visible
X-ray
Ultraviolet
X-ray
With a traditional optical telescope, the space between stars and
galaxies (the background) is completely dark. However, a sufficiently
sensitive radio telescope shows a faint background glow, almost exactly
the same in all directions, that is not associated with any star, galaxy, or
other object. This glow is strongest in the microwave region of the radio
spectrum. The CMB's serendipitous discovery in 1964 by American radio
astronomers Arno Penzias and Robert Wilson was the culmination of
work initiated in the 1940s, and earned them the 1978 Nobel Prize.
Doppler Effect


The motion of an object can be measured through a
change in the frequency of the waves emitted by the
object
The increase in pitch of an approaching police car is
caused by the compression of the sound wave

The pitch decreases as the police car moves away
Doppler Shift

In astronomy, the same
effect happens to light
waves

A source that is moving
away will appear redder
(redshift)

A source that is moving
toward us will appear
bluer (blueshift)

Note: Only objects
moving toward or away
from us (radial motion)
will show this effect
EM Spectrum HW:
 p.
389 # 1-3, 31-35
Powerpoint Credits
 J.
Beauchemin 2009 free online ppt
Image credits
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
http://www.antonineeducation.co.uk/New_items/MUS/images/Making6.gif
http://www.geocities.com/researchtriangle/campus/6791/einste
in12.jpg
http://abyss.uoregon.edu/~js/glossary/wave_particle.html
http://www.astro.princeton.edu/~gk/A402/electromagnetic_spe
ctrum.jpg
http://science.hq.nasa.gov/kids/imagers/ems/radio.html
http://www.nentjes.info/Palace/radio-6.gif
http://www.mobilewhack.com/motorola-h12-bluetoothheadset.jpg
http://www.stuffintheair.com/radar-real-time-weather.html
http://www.imaging1.com/gallery/images/AV%20Night%20visi
on%20goggles.jpg
http://www.global-b2bnetwork.com/direct/dbimage/50329753/Study_Remote_Control
.jpg
http://www.georgiaprismaward.com/The_Prism_Story_files/PRI
SM%20brand%20imagemed.jpg
http://science.hq.nasa.gov/kids/imagers/ems/uv.html
Image Credits
13.
14.
15.
16.
17.
18.
19.
20.
http://farm3.static.flickr.com/2385/2381723771_12548f
4bd1.jpg?v=1217429879
http://intamod.com.au/images/uv2.JPG
http://science.hq.nasa.gov/kids/imagers/ems/xrays.html
http://www.sciencelearn.org.nz/var/sciencelearn/storage
/images/contexts/see_through_body/sci_media/neck_x_r
ay/17945-5-eng-NZ/neck_x_ray_full_size_portrait.jpg
http://www.epinion.eu/wordpress/wpcontent/uploads/2008/05/airport-security1.jpg
http://science.hq.nasa.gov/kids/imagers/ems/gamma.ht
ml
http://www.aboutnuclear.org/print.cgi?fC=Food
http://www.roswellpark.org/files/1_2_1/brain_spinal/ga
mma%20knife%204c.jpg