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Good Morning! 7/7/2017 •Starter: What is Light? ( you need to write an answer for this one) •Goal: get some understanding of what light is and the spectrum of electromagnetic waves. •Today we continue our discussion on Waves, simply moving into a new area of waves. First we need to finish the worksheet from yesterday on Sound waves. Link to PPT We are going to split up and do the worksheet on the laptops The rest will be going through a Powerpoint (.ppt) on the screens. For those going to the laptops you will be going to the usual place. Science Shares Folders Durand then open the word doc. “EMSpectrumLink” Light is a crazy thing that we may never understand, but let me tell you what we do know. •Light travels as a wave, a transverse, Electromagnetic Wave. •It can behave as a particle •It travels faster than anything in the universe! •It is impossible for us to travel faster than the speed of light. The Back Story Why does light travel so fast? What are electromagnetic waves? 12.1 Waves and Particles • The difference between a wave and a particle might seem obviousa wave is a disturbance that carries energy, and a particle is a piece of matter. • However, in reality the difference is not so clear. What are electromagnetic waves? 12.1 Waves and Particles • In 1887, Heinrich Hertz found that by shining light on a metal, electrons were ejected from the metal. • Hertz found that whether or not electrons were ejected depended on the frequency of the light and not the amplitude. What are electromagnetic waves? 12.1 Waves and Particles • Because the energy carried by a wave depends on its amplitude and not its frequency, this result was mysterious. • Years later, Albert Einstein provided an explanationelectromagnetic waves can behave as a particle, called a photon, whose energy depends on the frequency of the waves. What are electromagnetic waves? 12.1 Particles as Waves • Because electromagnetic waves could behave as a particle, others wondered whether matter could behave as a wave. • If a beam of electrons were sprayed at two tiny slits, you might expect that the electrons would strike only the area behind the slits, like the spray paint. What are electromagnetic waves? 12.1 Particles as Waves • Instead, it was found that the electrons formed an interference pattern. • This type of pattern is produced by waves when they pass through two slits and interfere with each other. Particles as Waves • Water waves produce an interference pattern after passing through two openings. • It is now known that all particles, not only electrons, can behave like waves. Electromagnetic Waves Believe it or not, you are being “showered” all the time, not by rain but by waves. What Is an Electromagnetic Wave? An electromagnetic wave consists of vibrating electric and magnetic fields that move through space at the speed of light. How do sunglasses work? An analogy for sunglasses The Nature of Electromagnetic Waves Electromagnetic Waves Click the Video button to watch a movie about electromagnetic waves. Waves of the Electromagnetic Spectrum Electromagnetic Waves Activity Click the Active Art button to open a browser window and access Active Art about electromagnetic waves. Waves of the Electromagnetic Spectrum What Is the Electromagnetic Spectrum? The electromagnetic spectrum is the complete range of electromagnetic waves placed in order of increasing frequency. Electromagnetic Waves Waves of the Electromagnetic Spectrum Electromagnetic Spectrum Click the Video button to watch a movie about the electromagnetic spectrum. Please turn in your Worksheet on Electromagnetic Spectrum Radio and Television In AM transmissions, the amplitude of a radio wave is changed. In FM transmissions, the frequency is changed. Wireless Communication Comparing Frequencies In the cellular phone system, cellular phones transmit and receive radio waves that travel to the nearest tower.