Theres a whole lot of light out there The Electromagnetic Spectrum The electromagnetic spectrum is made up of visible and nonvisible light Electromagnetic waves are produced by stars and galaxies ID: 449083
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Slide1
The Electromagnetic Spectrum
There’s a whole lot of light out there!Slide2
The Electromagnetic Spectrum
The electro-magnetic spectrum is made up of visible and nonvisible light.Slide3
Electromagnetic waves are produced by stars and galaxies.
Examples from SpaceSlide4
Wavelengths
The distance from one wave crest to the next. The
CREST
is the top of the wave and the
TROUGH
is the bottom of the wave.Slide5
Frequency
Frequency is the number of waves to cross a point in one second.Radio waves have the lowest frequency.
Gamma rays have the highest frequency.Slide6
Frequency vs. Wavelength
Low frequencies = LONG wavelengthsHigh frequencies = SHORTER wavelengths
Radio waves have a ____ frequency and ________ wavelengths.
Gamma rays have a ____ frequency and ________ wavelengths.Slide7
Frequency vs. Wavelength
Low frequencies = LONG wavelengths
High frequencies = SHORTER wavelengths
Radio waves have a
LOW
frequency and
LONG
wavelengths.
Gamma rays have a
HIGH
frequency and
SHORT
wavelengths.Slide8
What we are most sensitive to
The radiation to which our eyes are most sensitive has a wavelength near the middle of this range, in the yellow-green
region of the spectrum.Slide9
Light we are most sensitive to
It is no coincidence that this wavelength falls within the range of wavelengths at which the Sun emits most of its electromagnetic energy—our eyes have evolved to take greatest advantage of the available light.Slide10
The Speed of Light
Electromagnetic waves travel VERY FAST – around 300,000 kilometres per second (the speed of light).At this speed they can go around the world 8 times in one second.Slide11
RADIO WAVES
Have the
longest
wavelengths and
lowest
frequencies of all the electromagnetic waves
.
Used in TV signals, remote control devices like car alarms, and garage door openers
Global Positioning Systems (GPS) measure the time it takes a radio wave to travel from several satellites to the receiver, determining the distance to each satelliteSlide12
Radio Waves
A radio picks up radio waves through an antenna and
turns it into
sound waves.
Each radio station in an area broadcasts at a different frequency.
# on radio dial tells frequency.
Radio waves disturb electromagnetic fields.
MRI
(MAGNETIC RESONACE IMAGING)
Uses Short wave radio waves with a magnet to create an image.Slide13
Microwaves
Have the shortest wavelengths and the highe
st
frequency of the
radio waves.
Used in microwave ovens
The waves are absorbed by water, fat, or sugar in the food causing them to vibrate which in turn transfers energy in the form of heat to the food.
RADAR
(
Ra
dio
D
etection
a
nd
R
anging)
Used to find the speed of an object by sending out radio waves and measuring the time it takes them to return.Slide14
Infrared Rays
Infrared
= below red
Shorter wavelength and higher frequency than microwaves.
Often called “heat rays”
You can feel the longest ones as warmth on your skin
Warm objects give off more heat energy than cool objects
.Slide15
Thermogram
—a picture that shows regions of different temperatures in the body. Temperatures are calculated by the amount of infrared radiation given off.
Therefore people give off infrared rays.
Heat lamps give off infrared waves.Slide16
Ultraviolet Rays
Shorter wavelength and higher frequency than visible light
Carry
more energy
than visible light
Used to
kill bacteria.
(Sterilization of equipment)
Too much can cause skin cancer.
Use sun block to protect against (UV rays)
Causes skin to produce Vitamin D which is good for teeth and bones.
Some insects see ultraviolet rays which helps them to locate nectar.Slide17
X- RAYS
Shorter wavelength and higher frequency than UV-rays.
Carry a great amount of energy.
Can penetrate most matter.
Bones and teeth
absorb
x-rays. (The light part of an x-ray image indicates a place where the x-ray was absorbed)
Too much exposure
can cause cancer
(lead vest protects organs from unnecessary exposure)Slide18
GAMMA RAYS
Shorter wavelength and higher frequency than X-rays
Carry the
greatest amount of energy
and penetrate the most.
Used in
radiation treatment
to kill cancer cells.
Can be very harmful if not used correctly.
Exploding nuclear weapons emit gamma raysSlide19
Brief SUMMARY
A.
All electromagnetic waves
travel at the same speed. (300,000,000 meters/second) in a vacuum.
B. They all have different
wavelengths
and different
frequencies.
Long wavelength
-lowest frequency
Short wavelength highest frequency
The higher the frequency the
higher the energy.Slide20
Homework:
Pg. 147-152 and test on Friday!