1. Electromagnetic Waves
Part 1: What are EM Waves?

2. There are two main categories of waves.
Review: Type of Waves
There are two main categories of waves.
Mechanical
e.g. water, sound, seismic waves
Waves that transfer energy through matter.
Require a substance (called a medium) to travel through.
Electromagnetic
e.g. light, radio, ultraviolet, x-rays
Waves that transfer energy through a field.
DO NOT require a substance (a medium) to travel through.

3. Electromagnetic Waves (EM)
Electromagnetic (EM) waves are very different than mechanical waves.
EM waves are disturbances that
transfer energy through a field –
They do NOT require atoms (matter).
The two main sources of EM waves are stars like the Sun, and human technology.

4. Characteristics of EM Waves
EM waves do not need a medium.
EM waves are able to travel through space.
EM waves all travel at the same incredible speed: 300,000 km/s.
EM waves have the same amplitude but different wavelengths and frequencies.
EM waves are organized by their unique frequencies on the EM spectrum.

5. Speed of EM Waves EM waves travel at 300,000 km/s.
EM Wave From NYC To… Time (s)____
Washington DC
Sydney, Australia
Around the Earth
Moon
Sun (8.5 min)

6. Electromagnetic Waves
Part 2: The Electromagnetic Spectrum

7. Electromagnetic Spectrum
What is the electromagnetic spectrum?
The EM spectrum is a family of EM waves
organized by their frequency, which is the
amount of energy that they carry.
Visible
Radio
Microwaves
Infrared
Ultraviolet
X rays
Gamma Rays

8. shorter wavelength more energy longer wavelength less energy
radio waves
microwaves
infrared light
visible light
ultraviolet light
x-rays
gamma rays
longer wavelength less energy

9. Radio Waves
Have the longest wavelengths, the lowest frequencies, and the lowest energies
Travel easily through the atmosphere and through other materials
Uses: AM/FM radio, TV, remote controls, garage door openers, alarm systems, baby monitors

10. Radio and Television Signals
Radio waves carry information in different ways. AM FM TV
AM radio changes the amplitude to encode sound info
FM radio changes the frequency to encode sound info
TV uses AM waves for picture and FM waves for the sound

11. Microwaves
Shorter wavelengths than radio waves, with higher frequencies and energy
Travel easily through the atmosphere and through many other materials
Uses: microwave ovens, cell phones, RADAR, satellite communications

12. Cell Phones Cell phones use overlapping networks
A cell phone is a microwave transmitter & receiver.
Cell phones use overlapping networks
called cells, each with a tower in its center
that receives and transmits microwaves.

13. A cell phone is a microwave transmitter & receiver.
Cell Phones
A cell phone is a microwave transmitter & receiver.
Hello?

14. Microwaves These ovens use beams of microwaves to
Microwaves heat up food from the inside.
These ovens use beams of microwaves to
make H2O molecules vibrate and heat up.

15. Microwaves Cool Fact: The heating properties of microwaves was
Microwaves heat up food from the inside.
Cool Fact:
The heating properties of microwaves was
discovered when a RADAR analyst’s candy
bar melted in his pocket while working!
These ovens use beams of microwaves to
make H2O molecules vibrate and heat up.

16. Infrared Waves Infrared waves are often associated with heat.
Infrared waves are produced when a warm object radiates heat.
Can’t be seen by us, but they can be felt!
Uses: remote controls, thermographs, heat-sensing animals

17. A Sixth Sense? Pit vipers have special “pits” on their heads
Infrared light is visible to some organisms.
Pit vipers have special “pits” on their heads
that let them detect heat from their prey.
Includes: rattlesnakes, cottonmouth, copperhead, fer-de-lance, bushmaster

18. These images are called thermographs.
Thermography
Infrared cameras used in medicine can reveal differences in temperature as bands of color.
These images are called thermographs.

19. Visible Light
Visible light is the part of the EM spectrum that human eyes can detect
Special cells in our eyes called cones, allow us to detect these wavelengths
Note: Visible light only makes up a very small part of the EM spectrum!

20. higher frequency more energy lower frequency less energy
red
orange
yellow
green
blue
indigo
violet
lower frequency less energy

21. Ultraviolet Light Ultraviolet rays occur naturally in sunlight
They reach Earth, but most are absorbed by the ozone layer
Can be dangerous since they can cause skin cancer and cataracts
Uses: sterilizing water and medical equipment

22. A Sixth Sense? Bees and other insects can detect
Ultraviolet light is visible to some insects.
Bees and other insects can detect
the higher frequencies of UV light.

23. A Sixth Sense? Bees and other insects can detect
Ultraviolet light is visible to some insects.
Bees and other insects can detect
the higher frequencies of UV light.

24. X Rays Have very high frequencies and energy
Can penetrate most substances, including many human tissues
Uses: x-ray images, since the waves travel easier through soft tissues than hard tissues, like bone

25. X Rays
X rays allow doctors to see through softer human tissues to examine harder tissues like bones, teeth and other objects!

26. Gamma Rays Have the highest wavelengths and carry the most energy
Produced by stars and some radioactive materials on Earth
Can penetrate all human tissues, killing cells and creating cancerous cells
Uses: fighting tumors

27. Black holes release energy in gamma rays bursts.
Gamma Ray Bursts
Black holes release energy in gamma rays bursts.

28. Radio Infrared X rays Bee Hz Microwaves Ultraviolet Gamma Rays
Visible Light
Radio
Microwaves
Infrared
Ultraviolet
X rays
Gamma Rays
Building
Humans
Pinhead
Bacteria
Atoms
Bee
Nuclei Hz

29. Any Questions?