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Section 1- What are electromagnetic waves? Slide 2 WHAT DO CORDLESS PHONES AND MICROWAVE OVENS HAVE IN COMMON? Each emits electromagnetic waves. Remember A wave is a repeating disturbance or movement that transfers energy through matter or space. EXAMPLE Water waves Sound waves Both types of waves require matter to travel through (mechanical waves) Slide 3 Electromagnetic waves Electromagnetic waves are made by vibrating electric charges and can travel through space where matter is not present. The energy carried by electromagnetic waves is called radiant energy. EXAMPLE--Sun, fire All electromagnetic waves travel at 300,000 km/s in the vacuum of space. Slide 4 Electromagnetic waves Because light is an electromagnetic wave, the speed of electromagnetic waves in space is usually called the speed of light. However, when electromagnetic waves travel through matter, they slow down. The speed of a wave depends upon the material they travel through. Slide 5 Electromagnetic waves E. waves usually travel the slowest in solids, and the fastest in gases. MATERIALSPEED (KM/S) VACUUM300,000 AIR SLIGHTLY LESS THAN 300,000 WATER226,000 GLASS 200,000 Slide 6 SPEED OF SOUND VS. SPEED OF LIGHT SOUNDLIGHT 761 MPH (MILES PER HOUR) 186,283 MPS (MILES PER SECOND) Slide 7 Section 2- The Electromagnetic Spectrum Slide 8 The electromagnetic spectrum Electromagnetic waves have a wide variety of frequenciesThey might vibrate once each second or trillions of times each second. The entire range of electromagnetic wave frequencies is known as the electromagnetic spectrum. Various portions of the e. spectrum interact with matter differently. As a result, they are given different names. Slide 9 The electromagnetic spectrum The e. waves that humans can detect with their eyes, called visible light, are a very small portion of the entire e. spectrum. Devices have been built to detect other frequencies. EXAMPLE--Radio antennadetects radio waves; Geiger counterdetects gamma rays E. waves are described by different names depending on their frequency and wavelength. Slide 10 The electromagnetic spectrum Slide 11 Electromagnetic spectrum Slide 12 The electromagnetic spectrum RADIO WAVESMICROWAVES LLowest frequency WWavelengths greater than 1mm UUsed with radio, radar, and Magnetic Resonance Imaging (MRIalternative to x- rays) LLow frequency WWavelengths less than 1m UUsed with cell phones, satellite signals, and microwave ovens Slide 13 tECHNOLOGY RADIO--MRI MICROCELL TOWER Slide 14 Radio waves--radar Radar stands for Radio Detecting And Ranging. RADAR detects the position and movement of objects. Radio waves are transmitted toward an object, bounce off the object and return to a receiving antenna. By measuring the time required, the location of the object can be found. (REFLECTION) Where is RADAR used? Law enforcement; tracking aircraft, watercraft, spacecraft; weather; and sports Slide 15 Slide 16 TECHNOLOGY INFRARED--PHOTO INFRAREDHEAT SENSORS Slide 17 The Greenhouse effect Slide 18 Things that normally happen in geologic time are happening during the span of a human lifetime. national geographic-september 2004 CO2--#1 GREENHOUSE GAS Since 1979, ice has decreased 9% per decade. Slide 19 Temperature rising--infrared Slide 20 ICE MELTING--INFRARED Slide 21 SEA LEVEL RISING WEATHER TURNING WILD--INFRARED Slide 22 Maleisland capital of the maldives/indian oceanIf sea level rises 3 feet, they could be under water by the end of the century. Slide 23 The electromagnetic spectrum INFRAREDVISIBLE LIGHT Low frequency Wavelengths between 1mm and 750 billionths of a meter Every object emits infrared waveshotter objects emit more than cooler objects EXAMPLESTV remote, fire, computer, GLOBAL WARMING (i. waves used to read cds) Middle frequency Wavelengths range from 400 billionths to 750 billionths of a meter The only portion of the spectrum that is detected without an instrument Slide 24 TECHNOLOGY VISIBLE LIGHTLIGHT BULB-- INDOOR VISIBLE LIGHT---LIGHT BULB-- OUTDOOR Slide 25 The electromagnetic spectrumultraviolet waves High frequency Wavelengths from 400 billionths to 10 billionths of a meter UV waves are energetic enough to enter skin cells! Slide 26 THE ELECTROMAGNETIC SPECTRUM USEFUL UVSHARMFUL UVS Some exposure is healthyenables body to make Vitamin D (needed for healthy bones and teeth) Ability to kill bacteria on food or medical supplies Make some materials fluorescepolice use f. powder to show fingerprints Over exposure is unhealthycan cause sunburn, skin damage, and skin cancer OZONE layer stratosphere (composed of 3 oxygen atoms)vital to life on Earth, because it absorbs most of the Suns harmful UV waves Many countries are reducing their use of OZONE depleting chemicals (labelsNO CFCS Chlorofluorocarbons) Slide 27 TECHNOLOGY UV--FINGERPRINTS UV-PROTECTIONGLASS, SUNSCREENS Slide 28 The electromagnetic spectrum X-RAYSGAMMA RAYS Very high frequency Can travel through matter EXAMPLESDoctors, dentists, airports Highest frequency Can travel through matter EXAMPLESRadiation therapy, radioactive material (U-235) Slide 29 TECHNOLOGY X-RAY--MEDICALX-RAY--AIRPORT Slide 30 TECHNOLOGY GAMMA RAYS (U-235)NUCLEAR POWER PLANT GAMMA RAYSNUCLEAR MEDICINERADIATION THERAPY Slide 31 Section3RADIO COMMUNICATION Slide 32 RADIO Each station is assigned to broadcast at one particular radio frequency. The specific frequency of the e. wave that a radio station is assigned to is called the carrier wave. EXAMPLE--The carrier wave = 100.1 FM (100.1mHz)100,100,000 cycles per second; the carrier wave can be AM (amplitude modulation) or FM (frequency modulation) Slide 33 FMFREQUENCY MODULATION AMAMPLITUDE MODULATION FM88mHz to 108mHz (mHzmillions of cycles per second) AM535kHz to 1605kHz (kHzthousands of cycles per second) (CYCLES OR WAVELENGTHS) Slide 34 AM VS. FM AMMODIFYING AMPLITUDE (FREQENCY IS CONSTANT) FMMODIFYING FREQUENCY (AMPLITUDE IS CONSTANT) Slide 35 Television TV and radio transmissions are similar. At TV stations, sound and images are changed into electric signals. These signals are broadcast by carrier waves (AM/FM). Audio = FM Image = AM (CRT) Slide 36 Cell phones and pagers CELL PHONESPAGERS Use radio and microwaves TRANSCEIVER transmits and receives radio signals (use 2 frequencies to allow you to talk and listen at the same time Use radio and microwaves Transceivertransmits and receives radio signals (use 2 frequencies to allow you to talk and listen at the same time Slide 37 COMMUNICATIONS SATELLITES Currently more than 2,000 satellites orbit Earth What are satellites used for? 1. Communications 2. Weather 3. Military 4. TV 5. Radio 6. GPS (Global Positioning System)--Navigation Slide 38 Satellites A station broadcasts a high frequency microwave signal to the satellite. The satellite receives the signal, amplifies it, and transmits it back to Earth. The ground receiver dishes are rounded to help focus the microwaves. GROUND RECEIVER DISH Slide 39 Global Positioning System (GPS) LATITUDE, LONGITUDE, AND ELEVATION USES MICROWAVES GPS is a system of 24 satellites, 5 ground monitoring stations, and numerous receivers that provide details about your exact location at or above Earths surface. Slide 40 GPS Owned and operated by the U.S. Department of Defense, but the microwave signals they send out can be used by anyone. EXAMPLESAirplanes, ships, cars, and hikers Many automobile GPS receivers come withcolor display screens/maps, mileage to locations, and info for next exit Slide 41