1. The Nature of Electromagnetic Waves
Electromagnetic Waves – Transverse waves that consist of changing electric and magnetic fields.
Electromagnetic Radiation – The energy that is transferred by electromagnetic waves.
Speed of Electromagnetic Waves – 3 x 108 m/s in a vacuum
Light Waves or Particles? – Light has many of the properties of waves. But light can also act as a stream of particles.

2. The Nature of Electromagnetic Waves
5. Polarized Light – pg. 536 in Text – Light as a wave can pass through a polarized filter. PROOF OF LIGHT AS A WAVE!
6. Photon – When light acts as particles, the particles are called photons.
7. Photoelectric Effect – When a beam of light shines on some substances, it causes tiny particles called electrons to move. PROOF OF LIGHT AS PARTICLES!
All electromagnetic waves travel at the same speed (3 x 108 m/s) but they have different wavelengths and different frequencies.
Speed = Wavelength X Frequency

3. The Nature of Electromagnetic Waves

4. The Nature of Electromagnetic Waves
Radio Waves – EM waves with the longest wavelengths and lowest frequencies.
Microwaves – radio waves with the shortest wavelengths and highest frequencies. High energy radio waves! Used in cell phones & radar!
Infrared Rays – Heat waves - A thermogram, a picture taken by an infrared camera. Pg 543 in Text
Visible Light – The electromagnetic waves you can see.

5. The Nature of Electromagnetic Waves
13. Ultraviolet Rays – EM waves with wavelengths just shorter than those of visible light are ultraviolet rays. Ultraviolet –”beyond violet”
Too much U-V light exposure can cause skin cancer and/or cataracts.
X- rays – EM waves with very short wavelengths and higher frequencies than U-V rays. X-rays carry a lot of energy and can penetrate most matter.
Pg. 545 in Text – Why are the bones white?

6. The Nature of Electromagnetic Waves
Gamma Rays – These waves have the shortest wavelengths and highest frequencies of the EM spectrum. Because they carry the most energy (EM Radiation), these waves penetrate most matter. Pg 546 in Text - Cancer Therapy and Nuclear Medicine

7. The Nature of Electromagnetic Waves
Producing Visible Light: 16. Illuminated (Reflects) vs. Luminous (Gives Off) Your Shirt A Light Bulb 17. Incandescent Lights – glow when a tungsten filament inside them gets hot. Invented by Thomas Edison (1879). Gives off white light which is made of red, orange, yellow, green, blue & violet light. Most of the energy that enters these lights is given off as heat, not! light.

8. The Nature of Electromagnetic Waves
18.Fluorescent Lights – As electric current passes through the fill gas it causes the gas to emit u-v waves. When the u-v rays hit the powder coating the inside of the tube, the powder emits visible light. Unlike incandescent lights these lights give off most of their energy as light. They also last longer so they are less expensive.

9. The Nature of Electromagnetic Waves
19. Neon Lights - Consist of a sealed glass tube filled with neon. As electric current passes through the neon, particles of the gas absorb energy. The gas particles cannot hold the energy for very long. The energy is released in the form of light. This process is called Electric Discharge. Ex’s: Neon – Red, Helium – Pink, Krypton – Violet Sometimes the gases are put into colored glass tubes to produce other colors.

10. The Nature of Electromagnetic Waves
20. Sodium Vapor Lights – contain small amounts of sodium, neon and argon. These lights give off yellow light. Ex’s: Street and Parking Lot Lights They use very little electricity and give off a lot of light so they are very economical. 21. Tungsten-Halogen Lights – They have tungsten filaments and are filled with a halogen gas chlorine or fluorine. These lights give off a bright white light. Ex’s: Car Lights & Overhead Projector Lights

11. The Nature of Electromagnetic Waves
22. Bioluminescence – Occurs as a result of a chemical Rx. among proteins and oxygen in a living organism. Ex.’s Fireflies, Jellyfish, Deep sea Fish & Plants Wireless Communication 23. FM Radio vs. AM Radio – Frequency Modulation vs. Amplitude Modulation – bottom of Pg. 555 in Text 24. Television – Very high Frequency (VHF) vs. Ultra High Frequency (UHF) channels. Today most people get their T. V. signals via cable or satellite feeds.

12. The Nature of Electromagnetic Waves
25. Cellular Telephones (Cordless) – These phones transmit and receive signals using high – frequency radio waves (Microwaves). 26. The Global Positioning System (GPS) – Uses a group of two dozen communication satellites that work together using radio signals. These signals carry info that can give you your exact location on Earth’s surface or in the air.