 Electromagnetic wave (light) - a wave that consists of electric and magnetic fields.  These waves are produced when a charged particle oscillates  Unlike sound waves, all EM waves can travel through a vacuum, and travel at the speed of light (300,000,000 m/s).  EM waves are transverse waves.

 Electromagnetic Spectrum - an arrangement of EM waves in order of wavelength and frequency. Lowest Frequency = Lowest Energy: 1. Radio waves - most commonly used to transmit information (long wavelengths).

 2. Microwaves - first used for communication, now commonly used for heating food by causing water molecules to spin.

 3. Infrared Rays - these rays cannot be seen; they are felt as heat.

 4. Visible light - only portion visible to human eye. ROY G BIV  Put all 7 colors together to get “white” light

 5. Ultraviolet (UV) rays - can harm living cells causing cancer, cataracts and sunburn; absorbed by the ozone layer.  6. X - rays - absorbed by denser material (bone); excessive exposure is harmful.

 7. Gamma rays - these are the highest energy waves; they are emitted by radioactive materials and nuclear reactions

 Object moving TOWARDS you, wavelength is SHORTER, and shifted towards (appears) BLUE  Object moving AWAY from you, wavelength is LONGER, and shifted towards (appears) RED

 Example: ◦ On Jan 1, 2007, star A is observed with a wavelength of 535 nm ◦ On Jan 1, 2008, star A is observed with a wavelength of 545 nm 545nm – 535 nm = 10 nm shift Since the wavelength is increasing, the star must be moving AWAY from Earth

 Example: ◦ On Jan 1, 2007, star B is observed with a wavelength of 544 nm ◦ On Jan 1, 2008, star B is observed with a wavelength of 560 nm 556 nm – 544 nm = 16 nm shift Since the wavelength is increasing, the star must be moving AWAY from Earth Star B is moving faster

 Galaxies are moving away from us. So, at some point in the past they must have been closer to us.  14 billion years ago all of the galaxies in the universe occupied the same space, then the universe expanded rapidly.  BIG BANG THEORY

 Polarized light – light traveling in a single plane (all in one direction).  Ordinary light is mixture of light traveling in all directions. Polarization proves to us that light is a transverse wave.

Polarizing filter- material that allows light of only one direction to pass through. Light can be polarized by: 1. Reflecting off a smooth (nonmetallic) surface- Glare 2. Going through a polarizing filter (sunglasses) 3. Traveling through a crystal

 Applications:  Sunglasses: Glare reflecting off the road/water is polarized horizontally. Sunglass lenses are polarizing filters that are vertical to block the glare.

 LCD displays: Have two polarizing filters and glass plates with a liquid crystal in between. The liquid crystal will twist the light to allow dark and light places on a digital display.