Electromagnetic Spectrum
Wave - Review
 Waves are oscillations that transport energy.
 2 Types of waves:

Mechanical – waves that require a medium to travel
through


(sound, water, earthquakes)
Electromagnetic – waves that do not require a medium to
travel

(light)
Nature of Electromagnetic Waves
 Electromagnetic waves:
 are waves that travel without a medium. (They can travel
through empty space)
 They travel as vibrations in electrical and magnetic fields.

Speed of electromagnetic waves = 300,000,000 m/s


OR 300,000km/s
Takes light 8 minutes to move from the sun to earth {93 million
miles} at this speed.
Vocabulary Recap/Help Page
 Wavelength – The distance from crest to
crest of a wave. How long the wave is in
meters.
 Frequency – The number of waves that
pass a point in one second. Determines
the energy a wave has. Measured in
Hertz.
The Electromagnetic Spectrum
Electromagnetic Spectrum—Consists of waves at
all possible energies, frequencies, and wavelengths.
They are placed in order of increasing frequency
 So what do we notice about the wave as we move
further right on our diagram?
Radio Waves
 Radio waves have the longest wavelengths and lowest
frequency in the electromagnetic spectrum.

Wavelengths range from .1m to 100km
 Used by Radios, TVs, RADAR systems, Cell Phones
 Each radio station broadcasts in a different frequency
 Cellular phones use radio waves that are much smaller than TV
and FM radio waves.
Microwaves
 Used by long range communications,
microwaves, cell phones, pagers,
wireless networks, bluetooth, some
radar detectors.
 A microwave oven works by passing
microwave radiation, through the food,
and absorbed by the water/fat/sugar in
the food.


The energy causes the food particles to vibrate
against each other.
What’s the by product of things rubbing
together???

THERMAL ENERGY!
Infrared Light (below red)
 IR light from the sun is what keeps you warm
 Uses: remote controls, the bottom of your mouse,
night vision, target acquisition and tracking by the
military and short-ranged wireless communication.
Thermography:
test method that records
thermal patterns and
temperatures across
the surface of an object.

Warm objects give off
more energy than cold
objects

Visible Light
 The ONLY portion of the
EMS which can be detected
by the human eye.
 Some colors like brown,
pink, and magenta are not
present, but are a blend of
different wavelengths.

―White light‖ can be broken
down into each of the individual
colors by using a prism.
In science, primary colors are
Red, Blue, Green
 In art, primary colors are Red,
Blue, Yellow


WHY - http://www.weather.gov.hk/education/edu06nature/ele_colour_e.htm
Ultraviolet
(beyond violet)
 UV Light carries more energy than visible light
 Because of absorption in the atmosphere’s ozone
layer, more harmful types of UV light is blocked.
 This type of wave is what causes your skin to tan
and burn.





Used in tanning beds and black lights
Too much can cause skin cancer.
Some birds (birds of prey) and bees can see in the UV light spectrum
Used to kill bacteria. (Sterilization of equipment)
Causes your skin to produce vitamin D

(good for teeth and bones in moderation)
Use sun block to protect against (UV rays)
 UV rays are also what cause ―sun bleaching‖
when certain materials are left outside

X-Rays
 Waves longer than gamma,
shorter than ultraviolet.
Widely used in medical
imaging.

Carry a great deal of energy
 Has enough energy to pass
the less dense tissues but
not bone.

Teeth and Bones absorb x-rays
 Too much exposure can
cause cancer
Gamma Rays
 Smallest Wavelength (Highest Frequency) =
MOST ENERGY of entire EMS
 Gamma rays are the most dangerous form of
radiation emitted by a nuclear explosion
 Due to their high energy content, they are able to
cause serious damage when absorbed by living
cells.
 Naturally occur in:

Radioisotopes on Earth



(Radium, carbon-14, uranium-235, etc)
Fission and fusion reactions
produce it
Sun spots (most all of radiation
absorbed by atmosphere)
What type of electromagnetic waves have the most energy?
What type has the longest wavelength?
What type has the highest frequency?
What visible light has the longest wavelength?
What visible light has the lowest frequency?