1. Electromagnetic Waves 2017-2018
EQ: How are electromagnetic waves classified?

2. Electromagnetic Waves
You have seen waves travel in water, ropes, springs and have heard sound waves that travel through air and water.
All of these waves have something in common: they transfer energy through a medium.
Medium: material through which waves transfer energy (solids, liquids, gases)
Electromagnetic waves, however, are different.
Electromagnetic waves can transfer energy without a medium

3. Electromagnetic Waves
An electromagnetic wave is a transverse wave that transfers electrical and magnetic energy.
An electromagnetic wave consists of vibrating electric and magnetic fields that move through space at the speed of light.
Speed of light: 186,000 mi/sec or 300,000 km/sec

4. The Electromagnetic Spectrum
All electromagnetic waves travel at the same speed in a vacuum (no medium), but they have different wavelengths and different frequencies.
And just like we cannot hear all sounds, we cannot see all electromagnetic waves.
Some wavelengths are visible to our eyes (visible light), but
others our eyes cannot see (X-rays, radio waves, infrared rays)

5. The Electromagnetic Spectrum– Wavelength and frequency
Because the speed of all electromagnetic waves is the same (186,000 mps/300,000 mps), as the wavelength(the distance from one crest to the next) decreases(gets smaller), the frequency increases.
Wavelength – distance from crest to crest or trough to trough
Frequency – number of complete waves passing past a certain point in a certain amount of time.

6. The Electromagnetic Spectrum– Wavelength and frequency
Waves with the longest wavelengths have the lowest frequencies.
Waves with the shortest wavelengths have the highest frequencies
The higher the frequency, the higher the energy it is.

7. The electromagnetic spectrum
The electromagnetic spectrum is the complete range of electromagnetic waves placed in order of increasing frequency.
The electromagnetic spectrum is made up of radio waves, infrared waves, visible light, ultraviolet rays, X-rays and gamma rays

8. Radio waves
Radio waves are the electromagnetic waves with the *longest wavelengths *lowest frequencies.
They include broadcast waves (for radio and television) and microwaves

9. Broadcast waves
Radio waves with longer wavelengths are used in broadcasting.
They carry signals for both radio and television programs.
A broadcast station sends out radio waves at certain frequencies
Antennas pick up the wave and converts the radio signal into an electrical signal.
The electrical signal is then converted into sound (and pictures as well on televisions)

10. Microwaves
The radio waves with the shortest wavelengths and the highest frequencies are microwaves.
Used for microwave ovens, cell phones, and RADAR.

11. Infrared rays
Infrared waves with wavelengths shorter than radio waves.
Use in heat lamps to keep food warm in restaurants, infrared cameras to help law enforcement find warm objects, and satellites in space use infrared cameras to study plant growth on Earth as well as the motion of clouds

12. Visible light
Electromagnetic waves that you can see are called visible light.
They make up only a small part of the electromagnetic spectrum.
Visible light waves have shorter wavelengths and shorter frequencies than infrared rays.

13. Visible light
Visible light waves with the longest wavelengths appear red in color.
As the wavelengths decrease, you see other colors of light.
The shortest wavelengths of visible light appear violet in color.

14. Ultraviolet rays
Electromagnetic waves with wavelengths shorter than those of visible light are called ultraviolet rays.
Ultraviolet rays have shorter frequencies than visible light, so they carry more energy.
The Sun’s rays are ultraviolet rays

15. Ultraviolet rays
The energy from ultraviolet rays is strong enough to burn your skin, cause cancer, damage your eyes or kill living cells.
Small doses are healthy for bones and teeth, as ultraviolet rays cause skin cells to produce Vitamin D

16. X-Rays
X-Rays have wavelengths just shorter and frequencies a little higher than ultraviolet rays.
Because of their high energy, X-rays can penetrate most matter.
This makes them useful to make images of teeth and bones, as the X-rays pass through the soft tissues but not the bony structures.
Too much exposure to X-rays can cause cat is why you wear a lead apron to protect your internal organs when you are having an X-ray made.
X-rays are also used to see if cracks exist in steel or concrete

17. Gamma Rays
Gamma rays are electromagnetic waves with the shortest wavelengths and shortest frequencies.
They are the most penetrating of all the electromagnetic waves.
Some radioactive and certain nuclear reactions produce gamma rays.
Gamma rays are used to kill cancer cells (radiation)