1. Electromagnetic Spectrum

2. Wave - Review Waves are oscillations that transport energy. 2 Types of waves:  Mechanical – waves that require a medium to travel through  (sound, water, earthquakes)  Electromagnetic – waves that do not require a medium to travel  (light)

3. Nature of Electromagnetic Waves Electromagnetic waves:  are waves that travel without a medium. (They can travel through empty space)  They travel as vibrations in electrical and magnetic fields.  Speed of electromagnetic waves = 300,000,000 m/s  OR 300,000km/s  Takes light 8 minutes to move from the sun to earth {93 million miles} at this speed.

4. Vocabulary Recap/Help Page Wavelength – The distance from crest to crest of a wave. How long the wave is in meters. Frequency – The number of waves that pass a point in one second. Determines the energy a wave has. Measured in Hertz.

5. The Electromagnetic Spectrum Electromagnetic Spectrum—Consists of waves at all possible energies, frequencies, and wavelengths. They are placed in order of increasing frequency So what do we notice about the wave as we move further right on our diagram?

6. Radio Waves Radio waves have the longest wavelengths and lowest frequency in the electromagnetic spectrum.  Wavelengths range from.1m to 100km Used by Radios, TVs, RADAR systems, Cell Phones  Each radio station broadcasts in a different frequency  Cellular phones use radio waves that are much smaller than TV and FM radio waves.

7. Microwaves Used by long range communications, microwaves, cell phones, pagers, wireless networks, bluetooth, some radar detectors. A microwave oven works by passing microwave radiation, through the food, and absorbed by the water/fat/sugar in the food.  The energy causes the food particles to vibrate against each other.  What’s the by product of things rubbing together???  THERMAL ENERGY!

8. Infrared Light (below red) IR light from the sun is what keeps you warm Uses: remote controls, the bottom of your mouse, night vision, target acquisition and tracking by the military and short-ranged wireless communication.  Thermography: test method that records thermal patterns and temperatures across the surface of an object.  Warm objects give off more energy than cold objects

9. Visible Light The ONLY portion of the EMS which can be detected by the human eye. Some colors like brown, pink, and magenta are not present, but are a blend of different wavelengths.  “White light” can be broken down into each of the individual colors by using a prism.  In science, primary colors are Red, Blue, Green  In art, primary colors are Red, Blue, Yellow  WHY - http://www.weather.gov.hk/education/edu06nature/ele_colour_e.htm

10. Ultraviolet (beyond violet) UV Light carries more energy than visible light Because of absorption in the atmosphere’s ozone layer, more harmful types of UV light is blocked. This type of wave is what causes your skin to tan and burn.  Used in tanning beds and black lights  Too much can cause skin cancer.  Some birds (birds of prey) and bees can see in the UV light spectrum  Used to kill bacteria. (Sterilization of equipment)  Causes your skin to produce vitamin D  (good for teeth and bones in moderation)  Use sun block to protect against (UV rays)  UV rays are also what cause “sun bleaching” when certain materials are left outside

11. X-Rays Waves longer than gamma, shorter than ultraviolet. Widely used in medical imaging.  Carry a great deal of energy Has enough energy to pass the less dense tissues but not bone.  Teeth and Bones absorb x-rays Too much exposure can cause cancer

12. Gamma Rays Smallest Wavelength (Highest Frequency) = MOST ENERGY of entire EMS Gamma rays are the most dangerous form of radiation emitted by a nuclear explosion Due to their high energy content, they are able to cause serious damage when absorbed by living cells. Naturally occur in:  Radioisotopes on Earth  (Radium, carbon-14, uranium-235, etc)  Fission and fusion reactions produce it  Sun spots (most all of radiation absorbed by atmosphere)

14. What type of electromagnetic waves have the most energy? What type has the longest wavelength? What type has the highest frequency? What visible light has the longest wavelength? What visible light has the lowest frequency?