Transcript Chapter 18 notes

Chapter 18
Electromagnetic Spectrum & Light
Electromagnetic Waves
 Electromagnetic Wave: is a transverse wave
consisting of changing electric and magnetic
fields.
 Draw picture: Page 533
 Carries energy from one place to another.
 Does not require a medium to travel
 Differ from mechanical waves by how they
are produced and travel
Electromagnetic wave
 Electromagnetic waves are created by
constantly changing electric or magnetic fields

Push/Pull effect that moves the waves
 Electromagnetic waves can travel through a
vacuum, empty space, or matter (medium)
 All travel at the same speed through a vacuum
 Speed is 3.0 X108 m/s (speed of light)
Wavelength & Frequency
 Electromagnetic waves vary in wavelength
and frequency (THIS IS HOW E.M. WAVES
ARE IDENTIFIED)
 Indirect relationship – as the wavelength
increases, the frequency decreases
 If you know the wavelength, you can calculate
its frequency
Speed
Frequency =
Wavelength
 Electromagnetic radiation behaves like a
wave and a stream of particles
 Photons are packets/particles of
electromagnetic energy
 Intensity is the rate at which a wave’s energy
flows through a given area
 Light intensity decreases as distance from the
light source increases
18.2 Electromagnetic Spectrum
 Electromagnetic Spectrum is the full range of
frequencies of electromagnetic radiation
 Each wave in the spectrum is characterized
by a range of wavelengths and frequencies.
 Waves, ranging from radio, infrared rays,
visible light, ultraviolet rays, x-rays, and
gamma rays
 Left Side of the spectrum
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Long Wavelength
Low frequency
Low energy
 Right Side of the spectrum
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Short Wavelength
High frequency
High Energy
 http://imagine.gsfc.nasa.gov/science/toolbox/
emspectrum1.html
Light spectrum and energy
https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&ved=0
ahUKEwiVwe2A7uDKAhXD6SYKHQG6CAIQjRwIBw&url=http%3A%2F%2Fww
w.drcruzan.com%2FChemistry_Atoms.html&psig=AFQjCNHDwezo1aa8525s0Bz
 Radio Waves: are used for the following:
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Television signals
Radio stations
Radar- give location of other objects (military)
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Speed guns that cops use
Microwaves- cooking
Have longest wavelengths and lowest
frequencies
 Infrared Rays: are used for the following:
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Heat sources: heat lamps used to keep food
warm
Thermo-grams: are pictures that show
differences in temperature
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Military use these
Hunters
Thermograms
 Visible Light: is located in the middle of the
electromagnetic spectrum (light)
 Visible light ranges from red to purple
 Copy chart on page 543
 Ultraviolet Rays: are used in the following
areas:
 Health
 Kill bacteria and micro organisms (hospitals)
 UV rays used as a disinfectant
 Sun: sunburns and skin cancer (sunscreen
for protection)
 X-RAYS: have the second highest frequency,
their radiation can hurt or kill living organisms
(overexposure)
 Broken bones
 Look in suitcases at airport
 Department of Transportation (Look inside of
trucks)
 Gamma Rays: the highest frequency and
energy levels on the spectrum
 Radiation from the sun
 Atomic blasts
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Health benefits
MRI pictures
Radiation treatment to kill cancer
Overexposure can cause death
 Incandescent Light: is produced when a
filament gets hot from the friction of electricity
passing through it
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Incandescent light gives off heat
Filament is made from tungsten
 Fluorescent Light: produces light by exciting a
phosphor and causing them to emit photons
 Does not emit much heat energy
 Requires less electricity than incandescent
 Does not give as much heat as incandescent
 Neon Light: is produced when electricity
passes through a noble gas
 Helium, Neon, Krypton, Argon
 Advertising
 Store signs
 USE LARGE AMOUNTS OF ELECTRICITY
 EXPENSIVE
Red shift blue shift /Doppler effect
http://www.lcse.umn.edu/specs/labs/images/doppler.gif
Red shift blue shift in space
 Redshift and blueshift describe how light
changes as objects in space (such as stars or
galaxies) move closer or farther away from
us. The concept is key to charting the
universe's expansion. –
 video
 See more at: http://www.space.com/25732-
redshift-blueshift.html#sthash.GoeViqqw.dpuf
 When an object moves away from us, the
light is shifted to the red end of the spectrum,
as its wavelengths get longer. If an object
moves closer, the light moves to the blue end
of the spectrum, as its wavelengths get
shorter.
- See more at: http://www.space.com/25732-redshift-blueshift.html#sthash.GoeViqqw.dpuf
https://alienspacesciencenews.files.wordpress.com/2013/04/blue-doppler-shifted-light-blue-shift-red-shift-spectra-visible-light-wow-data-line-22-signal-communication.jpg