Page 0: Page 1: LOGO ELECTROMAGNETIC SPECTRUM Edmund L. Benaojan, MM, PTRP Page 2: Brief review: Water and sound waves transfer energy from one place to another- they require a medium through which to travel. They are mechanical waves. Electric field-region in which charged particles can be pushed or pulled. Page 3: Nature of Electromagnetic Waves They are Transverse waves without a medium. (They can travel through empty space) They travel as vibrations in electrical and magnetic fields. Have some magnetic and some electrical properties to them. Speed of electromagnetic waves = 300,000,000 meters/second (Takes light 8 minutes to move from the sun to earth {150 million miles} at this speed.) Page 4: When an electric field changes, so does the magnetic field. The changing magnetic field causes the electric field to change. When one field vibrates—so does the other. RESULT-An electromagnetic wave. Page 5: Waves or Particles  Electromagnetic radiation has properties of waves but also can be thought of as a stream of particles.  Example: Light  Light as a wave: Light behaves as a transverse wave which we can filter using polarized lenses.  Light as particles (photons)  When directed at a substance light can knock electrons off of a substance (Photoelectric effect) Page 6: B. Waves of the Electromagnetic Spectrum  Electromagnetic Spectrum—name for the range of electromagnetic waves when placed in order of increasing frequency RADIO WAVES INFRARED RAYS ULTRAVIOLET RAYS GAMMA RAYS MICROWAVES VISIBLE LIGHT X-RAYS Page 7: RADIO WAVES A. Have the longest wavelengths and lowest frequencies of all the electromagnetic waves. B. A radio picks up radio waves through an antenna and converts it to sound waves. C. Each radio station in an area broadcasts at a different frequency. # on radio dial tells frequency. D. MRI (MAGNETIC RESONACE IMAGING)  Uses Short wave radio waves with a magnet to create an image Page 8: MRI of the Brain Page 9: AM=Amplitude modulation—waves bounce off ionosphere can pick up stations from different cities. (535kHz-1605kHz= vibrate at 535 to 1605 thousand times/second) + Page 10: FM=Frequency modulation—waves travel in a straight line & through the ionosphere--lose reception when you travel out of range. (88MHz-108MHz = vibrate at 88million to 108million times/second) + Page 11: Bands of Radio/TV/Microwaves Page 12: MICROWAVES Microwaves—have the shortest wavelengths and the highest frequency of the radio waves.  Used in microwave ovens. • Waves transfer energy to the water in the food causing them to vibrate which in turn transfers energy in the form of heat to the food.  Used by cell phones and pagers.  RADAR (Radio Detection and Ranging) • Used to find the speed of an object by sending out radio waves and measuring the time it takes them to return. Page 13: INFRARED RAYS  Infrared= below red  Shorter wavelength and higher frequency than microwaves.  You can feel the longest ones as warmth on your skin  Heat lamps give off infrared waves.  Warm objects give off more heat energy than cool objects.  Thermogram—a picture that shows regions of different temperatures in the body. Temperatures are calculated by the amount of infrared radiation given off. Therefore people give off infrared rays. Page 14: Page 15: VISIBLE LIGHT Shorter wavelength and higher frequency than infrared rays. Electromagnetic waves we can see. Longest wavelength= red light Shortest wavelength= violet (purple) light When light enters a new medium it bends (refracts). Each wavelength bends a different amount allowing white light to separate into it’s various colors ROYGBIV. Page 16: Page 17: ULTRAVIOLET RAYS Shorter wavelength and higher frequency than visible light Carry more energy than visible light Used to kill bacteria. (Sterilization of equipment) Causes your skin to produce vitamin D (good for teeth and bones) Used to treat jaundice ( in some new born babies. Too much can cause skin cancer. Use sun block to protect against (UV rays) Page 18: X- RAYS  Shorter wavelength and higher frequency than UV-rays  Carry a great amount of energy  Can penetrate most matter.  Bones and teeth absorb x-rays. (The light part of an x-ray image indicates a place where the x-ray was absorbed)  Too much exposure can cause cancer  Used by engineers to check for tiny cracks in structures.  The rays pass through the cracks and the cracks appear dark on film.  (lead vest at dentist protects organs from unnecessary exposure) Page 19: Page 20: GAMMA RAYS Shorter wavelength and higher frequency than X-rays Carry the greatest amount of energy and penetrate the most. Used in radiation treatment to kill cancer cells. Can be very harmful if not used correctly. Page 21: Using the EM waves to view the Sun Animation—View a Galaxy at different wavelengths Page 22: Brief SUMMARY A. All electromagnetic waves travel at the same speed. (300,000,000 meters/second in a vacuum. B. They all have different wavelength and different frequencies.  Long wavelength-lowest frequency  Short wavelength highest frequency  The higher the frequency the higher the energy. Page 23: Page 24: