Examples of Electromagnetic
Waves/Radiation
• Radio Waves (AM and FM radio waves andTV
signals)
• Cell phone communication links
• Microwaves
• Infrared radiation
• Light
• X-rays
• Gamma rays
Spring 2006
Physics 8; 2006
• What
distinguishesUCSD:
these
from one another? 3
•Electromagnetic (EM) Waves need
NO MEDIUM (matter) to travel.
•They are TRANSVERSE waves that travel
through EMPTY SPACE!!
•However, they can travel through a
medium (matter).
EM waves travel as VIBRATIONS in
ELECTRICAL and MAGNETIC FIELDS
Electromagnetic
waves are arranged from
longest to shortest
wavelength forming the
The Longer the wavelength,
the Lower the frequency =
Low energy. (Rule of Ls)
The sHorter the wavelength,
the Higher the frequency =
High energy. (Rule of Hs)
Low Frequency
That this set of waves passed by a point in one second. There are 5 waves in this
picture. The frequency of this wave is therefore 5 cycles per second (Hz).
High Frequency
This set of waves passed by the same point in one second. There are 13 waves in
this picture. The frequency of this wave is therefore 13 cycles per second (Hz).
Radio waves are divided into:FM,
AM,
VHF,
UHF
Microwaves
• Microwaves are a type of radio wave. They
have the shortest wavelength and the
highest frequency of the radio waves.
• Microwave ovens transfer energy to the
water in the food causing them to vibrate.
• Microwaves are also used
by cell phones and pagers!
A.
Radar

Radar (radio detection and ranging) devices
send out short pulses of microwaves, count the
time until they return, and then calculate the
distance to an object.
 Radar is used to monitor airplanes, ships, and to
track weather systems. Police use radar guns to
calculate the speed of drivers.
Infrared Rays
• Heat Lamps give off
infrared waves and so do
living things!!
• You can feel the longest
waves as warmth on your
skin!
• Used in remote controls
Infrared Lie-detection
Before the lie
After the lie
The military uses IR to see objects
it considers relevant
IR light penetrates fog and smoke better than
visible light.
Visible Light
ROYGBIV
Ultraviolet Rays
X-RAYS
• Great amounts of energy,
can penetrate through most
matter!
• Bones and teeth Absorb x-rays,
that is how we see them in the
x-ray picture.
• Too much can cause cancer!!
Gamma Rays
• Carry greatest amount of
energy and can penetrate
through most matter!!
• Used in radiation treatment to
kill cancer cells.
• Very harmful if not used
correctly!!!
How the EM Spectrum Helps
us Judge Distances in Space:
Because the Universe is so Vast,
interstellar distances are so great
that the light emitted from other
objects in space can take
upwards of millions of years to
reach us!!!
So how can we tell just how far away
an object is??????
Distances are measured in
Light Years – this is how far light
travels through space in 1 year
(about 6,000,000,000,000 miles).
So, we use specific types of
telescopes and satellites out in space to
take pictures of the EM waves and
scientists can then determine what type
they are, then judge how many light
years away the object is!
But still, how does this help us
see objects in space? Well…
Extremely smart scientists have
figured out that different types of
ElectroMagnetic waves travel through
our atmosphere at different frequencies
and wavelengths.
Scientists can determine where an
object is located by the type of EM wave
emitting through our atmosphere!!