1. Electromagnetic Waves
Waves of energy emitted from any accelerating charges
Any object that is above absolute zero emits electromagnetic waves
The entire range of possibilities is called the “Electromagnetic Spectrum”
Still confused? Then click What are electromagnetic waves?
To learn about the wavelength of photons click to the next slide. To move onto the EM spectrum click

2. Electromagnetic Waves
Wavelength is :
Where,
c is the speed of light (3 x 108 m/s in a vacuum)
λ is the wavelength in meters
f is the frequency in Hertz

3. What is this “photon” term you’re throwing in there?
A photon is a bundle (quantum) of light
A photon has energy equal to
Recall that
h is Plank’s constant
ν is the frequency of the radiation (wave)

4. What does a photon do?
Both magnetic and electric forces involve the exchange of photons
The photon has zero rest mass, but has momentum, can be deflected gravity, and can exert a force

6. TYPES OF ELECTROMAGNETIC WAVES
GAMMA RAYS
Emitted from the nuclei of atoms during radioactive decay or during high-speed collisions with particles.
Ionizing
Used in cancer treatment and for sterilization Sources: Cobalt 60, the inner core of the sun

7. X-RAYS
Emitted when an electron moves from certain excited states back down to its ground state, or when an electron that is moving very quickly is suddenly stopped
Two groups - long wavelength (soft x-rays) and shorter wavelength (hard x-rays)
Used for radiography (x-ray photography) and to look at materials in industry for defects
Sources:  emitted by heavy atoms after bombardment by an electron

8. ULTRAVIOLET Above the color violet
Three groups - UV A, UV B, and UV C.
“A” type: longest wavelength; least harmful
UV B and UV C are absorbed by DNA in cells 
Used by the body to produce vitamin D, to kill bacteria on objects, and for sun tanning
Sources:   Ultra hot objects 5000°C or more

9. VISIBLE LIGHT White light: combination of all the colors
Wavelength interval
Frequency interval
red
~ 625 to 740 nm
~ 480 to 405 THz
orange
~ 590 to 625 nm
~ 510 to 480 THz
yellow
~ 565 to 590 nm
~ 530 to 510 THz
green
~ 520 to 565 nm
~ 580 to 530 THz
cyan
~ 500 to 520 nm
~ 600 to 580 THz
blue
~ 430 to 500 nm
~ 700 to 600 THz
violet
~ 380 to 430 nm
~ 790 to 700 THz
White light: combination of all the colors
Rainbow: example of white light that has been separated into a continuous spectrum of colors
The names of colors are assigned in order of their wavelengths
Used for communications
(fiber optics)
Sources:   very hot objects

10. INFRARED Thought of as heat but is not always
Far infrared energy is heat energy.
All objects that have warmth radiate infrared waves
Easily absorbed and re-radiated. 
Used in remote controls,  surveillance, therapy of muscles
Sources:  Humans, the sun

11. MICROWAVES 1 mm-1 dm in length
Absorbed by water molecules – how microwave ovens heat food
Used in telecommunications and power transmission
Sources:  electric circuits, many stars, microwave ovens

12. RADIO WAVES 10 cm- 100,000+m in length
Only cosmic waves the reach the surface of the Earth
Cause of noise
Divided into smaller frequency dependent groups called bands  
Used for communications
Sources:  transmitters and sparks from motors

13. Polarization
Electric and magnetic fields which make up wave have preferred direction
Can be horizontal, vertical, circular, or elliptical
Most radio emission is unpolarized
To learn more click here

14. Polarization y Electric Field Electric Field Electromagnetic Wavex y z E
Horizontal Polarization
Electric Field
Magnetic Field
Electromagnetic
Wave
Vertical Polarization x y
Electric Field
Electromagnetic Wave
Magnetic Field

16. Why Do We Care About Radio Waves?
Gadgets- cell phones, microwaves, remote controls, garage door openers
Science- radio astronomy, atmospheric research