1. Electromagnetic Spectrum

2. Electromagnetic Waves
Electromagnetic waves come in many wavelengths and frequencies. Each one is useful in different ways.

3. Electromagnetic Spectrum
The electromagnetic spectrum is the range of all EM frequencies
The EM spectrum is a smooth, gradual progression from the lowest frequencies to the highest (and wavelengths)

5. Radio Waves
Waves that have the longest wavelength, the lowest frequency, and lowest energy
Travel easily through the atmosphere and materials
Radio waves are broadcasted by a transmitter where a receiver picks up the signals and converts it to sound waves
Radio stations use different frequencies so they don’t get crossed

6. Radio Waves
Two ways to modulate radio wave is by changing the amplitude and varying the frequency
Amplitude is used for AM
Frequency is used for FM
Televisions also use radio waves…they use AM signals for the picture and FM for the sound

7. Microwaves
Have shorter wavelengths, higher frequencies, and higher energy than other radio waves
Important uses of microwaves are radars and cell phones
Radars (WWII) transmits microwaves, receives reflections, and converts it into visual images
Radar led to the invention of the microwave oven

8. Microwaves
Your cell phone is actually a radio transmitter and receiver that uses microwaves
Sends and receives signals from a tower and is where the signals come together and allow you to connect with other person

9. Infrared Light
Found between microwaves and visible light, is the type of EM waves most often associated with heat
You cannot see infrared light, but you can feel the results
Examples: Warming lights at restaurants and your toaster

10. Visible Light
Part of the EM spectrum that humans can see and is the smallest part of the spectrum
The longest wavelength is “red” and the shortest is “violet”
The visible light from the sun is white light (all wavelengths are combined)

11. Visible Light The range of colors is called the visible spectrum

12. Visible Light used in many ways
Vision
Find food and other survival activities
Plants need it to make their food
Can you think of anything else?

13. Where does it come from? Most of it comes from the sun
The production of light by materials at high temperatures is called incandescence
Other sources include: Lightening and Fire

14. Living things produce light
Luminescence is the production of light without the high temperatures needed for incandescence.
The production of light by living organisms is called bioluminescence.
Produce by chemical reactions and not intense heat
Insects, worms, fish, squid, jellyfish, bacteria, and fungi

15. Human produced visible light
First was fire
Electrical lighting in late 1800’s (used tungsten) was known as incandescent bulbs
Fluorescence bulbs
Use gas instead of a filament
Neon lights (diff gases produce diff colors)
LED’s uses a semiconductor that regulates electric current to produce light

16. LED’s Light-emitting diodes
Idea came from the bioluminescence of animals
Light that produces little heat and uses almost all of its electrical energy to make light instead of the thermal energy
Not easily broken

17. Ultraviolet Light (radiation)
Has frequencies above those of visible light and partially below those of x-rays
Carries more energy than visible light
Waves can damage skin and eyes (cause sunburn)
Used to: sterilize medical equipment, kill harmful bacteria, produce vitamin D, treat skin problems and other medical conditions

18. X-rays Very high frequencies and energy Produced by sun and stars
Pass through soft tissue but is absorbed in dense matter, like bones
Over exposure to x-rays can cause cancer
Lead can block these types of EM waves

19. Gamma Rays Highest frequencies and energy of all the EM waves
Produced by sun and stars and some radioactive substances
Gamma rays kill normal cells and cause cancer cells to develop
However, doctors can use gamma rays to kill cancer cells and fight tumors when carefully controlled

21. Short Story For homework:
Write a short story in which the characters use or are affected by each of the different kinds of EM waves
Complete on a separate sheet of paper because you will turn it in