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Electromagnetic Spectrum Radio Waves Gamma Rays The Parts of the E.M.S. Radio Waves Microwaves Infrared Waves Visible Light UV Light X Rays Gamma Rays Why Are These Waves Alike? All these waves travel fast, much faster than sound They can travel through a vacuum or through space (no media is necessary) They are all transverse waves They transfer energy by radiation Lets Sketch the Spectrum Example A deep heat machine like the one used in a personal trainers office has a common frequency used of 27.33 MHz. What is the wavelength of this radiation? Example 2 If the north star which is 6.44 x 1018 m away were to burn out, in what year would we stop being able to view the star in our sky? Example 3 A wave has a wavelength of 4.0 x 10-7 m and a speed of 2.5 x 10 8 m/s in a particular material. A) What is its frequency in this material? B) The frequency of the wave does not change as the wave moves from one material to another. Find the wavelength of this wave in a vacuum. Radio Waves Long wavelengths Low frequencies Used in television and cell phones. Also FM and AM Using your voice, computers or other device, you can change radio wave frequencies and amplitudes. This is called Modulation. Microwaves Radio waves with the highest frequency and energy are microwaves Used in communication Also used in cooking. Microwave ovens transfer energy to the food, causing the molecules to move around (kinetic energy) and thus heating the item Infrared Radiation Wavelength is slightly longer than visible light, so we cannot see them. The sun emits a large amount of I.R. radiation. Warmer objects give off more radiation than cold objects Tumors give off more heat than regular tissue, so infrared cameras are useful. Visible Radiation Also called ____________? When the sun emits radiation with frequencies in the range of visible light, this radiation is viewable by humans Light can cause chemical reactions like photosynthesis. The Colors in the Visible Spectrum Red/ Orange/ Yellow/ Green/ Blue/ Indigo/ Violet ROYGBIV UV Radiation High energy waves Greater penetrating power UV lamps can be used to kill bacteria and sterilize surgical instruments Sunscreens are used to help protect us from sunburns which may lead to skin cancer What natural filter helps protect us? X-Rays Carry high energy X-rays can travel through skin and muscles, but once the waves hit a more dense area they become absorbed. The photograph is a negative, and b/c the bone absorbs the rays, it shines brighter Gamma Rays Highest frequency and smallest wavelength in the spectrum They come from the nuclei of radioactive atoms In high concentrations, they can destroy human cells and can be used to kill cancer cells In determining the distance to a cloud, a meteorologist in a TV station uses radar and notes it takes 0.24ms between the sending and return of a radar pulse. How far away is the cloud?