Electromagnetic Spectrum
How are colors of visible light different?
• What makes red light look red? Or blue look blue?
The wavelength determines what color we see
•Red has the longest
wavelength of visible
light
•Violet has the shortest
wavelength of visible
light
Vocabulary 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.
Electromagnetic Spectrum!!!
Radio Waves
• Radio waves have the
longest wavelengths
and lowest frequency in
the electromagnetic
spectrum.
• Radar uses radio waves
and reflections to
detect distances
Microwaves
• A microwave oven works
by passing microwave
radiation, through the
food.
• The energy causes the
water molecules to
vibrate against each
other.
• What’s the by product of
things rubbing
together???
Infrared Light (below red)
• Thermography: test
method that records
thermal patterns and
temperatures across the
surface of an object.
• Uses: night vision,
target acquisition and
tracking by the military
and short-ranged
wireless communication.
Visible Light
• The portion of the
spectrum 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.
violet
380–450 nm
blue
450–495 nm
green
495–570 nm
yellow
570–590 nm
orange
590–620 nm
red
620–750 nm
Ultraviolet (beyond violet)
• UV light has a wavelength
shorter than visible light but
larger than X-ray.
• 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 burn.
Your skin tans in an effort to
protect itself from continued
exposure.
X-Rays
• Waves shorter than gamma,
longer than ultraviolet.
Widely used in medical
imaging.
• Black regions are where
Xrays pass through, dense
tissues and bones come back
white. Barium Sulfate used to
absorb x-rays as well.
• Also given off by stars –
telescopes detect and
interpret these into images
• Smallest Wavelength
(Highest Frequency) =
LOTS of Energy
• 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.
• Useful in cancer
treatments and
radioactive tracers
Gamma Rays
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?
Waves that we CANNOT see?
• Visible light is just a tiny part of the
many types of waves in the
electromagnetic spectrum
• We cannot see wavelengths longer
than red, or shorter than violet!