1. Which day has the MOST sunlight in the United States?
March 25
June 18
September 26
December 19

3. Electromagnetic Waves
Waves of the Electromagnetic Spectrum
Electromagnetic Waves
Believe it or not, you are being “showered” all the time, not by rain but by waves. Electromagnetic waves!

4. Electromagnetic Waves
Waves of the Electromagnetic Spectrum
Electromagnetic Waves
An electromagnetic wave consists of vibrating electric and magnetic fields that move through space at the speed of light (186,000 miles per second!).
The energy that is transferred by electromagnetic waves is called electromagnetic radiation.

5. Electromagnetic Waves
Waves of the Electromagnetic Spectrum
Electromagnetic Waves
Electromagnetic waves are transverse waves. They move up and down or side to side.
The distance from the crest of one wave to the crest of the next wave is the wavelength.
The number of these waves that pass a given point in a certain amount of time is the wave’s frequency.

6. Electromagnetic Waves
Waves of the Electromagnetic Spectrum
Electromagnetic Waves
The Sun (and every star) gives off electromagnetic radiation.
On Earth, humans use different types of electromagnetic radiation for different purposes.
Humans can detect some types electromagnetic radiation: visible light and infrared radiation (heat).
But there are other types of electromagnetic radiation that humans can’t detect: radio waves, microwaves, ultraviolet radiation, x-rays, and gamma rays.
All of these types of radiation can travel through space at the speed of light.

7. What Is the Electromagnetic Spectrum?
Waves of the Electromagnetic Spectrum
What Is the Electromagnetic Spectrum?
The electromagnetic spectrum is the complete range of electromagnetic waves placed in order of decreasing wavelength (increasing frequency).
Notice that the shorter the wavelength, the higher the frequency.

8. What Is the Electromagnetic Spectrum?
Waves of the Electromagnetic Spectrum
What Is the Electromagnetic Spectrum?
Here’s an easy way to remember the order of electromagnetic waves by decreasing wavelength (increasing frequency):
Rabbits (radio)
Mate (microwaves)
In (infrared)
Very (visible light)
Unusual (ultraviolet)
(are)
eXpensive (x-rays)
Gardens (gamma rays)

9. What Is the Electromagnetic Spectrum?
Waves of the Electromagnetic Spectrum
What Is the Electromagnetic Spectrum?
The only difference between the different electromagnetic waves is their wavelength and the amount of energy they carry. There is a relationship between wavelength, frequency, and energy.
REMEMBER IT!!
long wavelength = low frequency = low energy
AND
short wavelength = high frequency = high energy

10. What Is the Electromagnetic Spectrum?
Waves of the Electromagnetic Spectrum
What Is the Electromagnetic Spectrum?

11. What Is the Electromagnetic Spectrum?
Waves of the Electromagnetic Spectrum
What Is the Electromagnetic Spectrum?
Radio Waves
Radio waves are the electromagnetic waves with the longest wavelengths, lowest frequency, and lowest energy.
On Earth, broadcast stations use radio waves to send out radio and TV signals.

12. What Is the Electromagnetic Spectrum?
Waves of the Electromagnetic Spectrum
What Is the Electromagnetic Spectrum?
Microwaves
Microwaves are actually a type of radio wave with slightly shorter wavelengths and higher frequencies.
Microwave radiation is used in microwave ovens to heat food. It is also used in cell phone communication and police radar (Radio Detection and Ranging).

13. What Is the Electromagnetic Spectrum?
Waves of the Electromagnetic Spectrum
What Is the Electromagnetic Spectrum?
Infrared Rays
Infrared rays have shorter wavelengths, higher frequencies, and higher energy than radio waves.
Humans detect infrared radiation as heat.
An infrared camera takes pictures using infrared rays instead of visible light. These are called thermograms.

14. Electromagnetic Waves
The Nature of Electromagnetic Waves
Electromagnetic Waves
Click below to watch a movie about infrared radiation.

15. What Is the Electromagnetic Spectrum?
Waves of the Electromagnetic Spectrum
What Is the Electromagnetic Spectrum?
Visible light
Visible light has shorter wavelengths, higher frequencies, and higher energy than infrared rays.
This type of radiation is detectable by human eyes.
The colors in the visible spectrum include red, orange, yellow, green, blue, indigo, and violet.
White light is a mixture of all the colors.

16. What Is the Electromagnetic Spectrum?
Waves of the Electromagnetic Spectrum
What Is the Electromagnetic Spectrum?
Ultraviolet radiation
Ultraviolet radiation (UV) has shorter wavelengths, higher frequencies, and higher energy than visible light.
A small amount of UV radiation is beneficial to humans for producing vitamin D.
However, too much exposure to UV radiation can cause skin cancer.

17. What Is the Electromagnetic Spectrum?
Waves of the Electromagnetic Spectrum
What Is the Electromagnetic Spectrum?
X-rays
X-ray radiation has very short wavelengths, high frequencies, and higher energy than UV radiation.
Because they are such a high-energy radiation, x-rays can penetrate most matter.
X-rays are used to make pictures of bones and teeth inside the human body.
Too much exposure to x-rays can cause cancer.

18. What Is the Electromagnetic Spectrum?
Waves of the Electromagnetic Spectrum
What Is the Electromagnetic Spectrum?
Gamma rays
Gamma rays have the shortest wavelengths, highest frequencies, and highest energy of the electromagnetic spectrum.
Gamma rays are generated by radioactive atoms and nuclear explosions. They are the most penetrating of all electromagnetic radiation. Gamma rays can penetrate 6 feet of concrete!
Gamma rays can kill living cells, which doctors use to their advantage. Using gamma rays, surgeons can precisely target and kill cancer cells in the body.
Uncontrolled exposure to gamma radiation is deadly.

19. Electromagnetic Waves
Waves of the Electromagnetic Spectrum
Electromagnetic Waves
Electromagnetic waves are all around you–in your home, your neighborhood, and your town.

20. Electromagnetic Waves
Waves of the Electromagnetic Spectrum
Electromagnetic Waves
The electromagnetic waves with the highest energy can penetrate and damage the cells of living things.
These include ultraviolet radiation, x-ray radiation, and gamma radiation.
Although some UV radiation reaches the surface of Earth, the atmosphere of Earth blocks all x-ray and gamma radiation.