electromagnetic spectrum tattnall county schools 电磁频谱塔特纳尔县学校课件

The Electromagnetic Spectrum S8P4a Electromagnetic waves come in many wavelengths and frequencies. Each one is useful in different ways. Electromagnetic Waves /kids/imagers/ems/index.html Electromagnetic Spectrum The electromagnetic spectrum is the range of all EM frequencies The EM spectrum is a smooth, gradual progression from the lowest frequencies to the highest (and wavelengths) Radio Waves Waves that have the longest wavelength, the lowest frequency, and lowest energy Travel easily through the atmosphere and materials Radio waves are broadcasted by a transmitter where a receiver picks up the signals and converts it to sound waves Radio stations use different frequencies so they dont get crossed Radio Waves Two ways to modulate radio wave is by changing the amplitude and varying the frequency Amplitude is used for AM Frequency is used for FM Televisions also use radio wavesthey use AM signals for the picture and FM for the sound Microwaves Have shorter wavelengths, higher frequencies, and higher energy than other radio waves Important uses of microwaves are radars and cell phones Radars (WWII) transmits microwaves, receives reflections, and converts it into visual images Radar led to the invention of the microwave oven Microwaves Your cell phone is actually a radio transmitter and receiver that uses microwaves Sends and receives signals from a tower and is where the signals come together and allow you to connect with other person Infrared Light Found between microwaves and visible light, is the type of EM waves most often associated with heat You cannot see infrared light, but you can feel the results Examples: Warming lights at restaurants and your toaster Visible Light Part of the EM spectrum that humans can see and is the smallest part of the spectrum The longest wavelength is “red” and the shortest is “violet” The visible light from the sun is white light (all wavelengths are combined) Visible Light The range of colors is called the visible spectrum Visible Light used in many ways Vision Find food and other survival activities Plants need it to make their food Can you think of anything else? Where does it come from? Most of it comes from the sun The production of light by materials at high temperatures is called incandescence Other sources include: Lightening and Fire Living things produce light Luminescence is the production of light without the high temperatures needed for incandescence. The production of light by living organisms is called bioluminescence. Produce by chemical reactions and not intense heat Insects, worms, fish, squid, jellyfish, bacteria, and fungi Human produced visible light First was fire Electrical lighting in late 1800s (used tungsten) was known as incandescent bulbs Fluorescence bulbs Use gas instead of a filament Neon lights (diff gases produce diff colors) LEDs uses a semiconductor that regulates electric current to produce light LEDs Light-emitting diodes Idea came from the bioluminescence of animals Light that produces little heat and uses almost all of its electrical energy to make light instead of the thermal energy Not easily broken Ultraviolet Light (radiation) Has frequencies above those of visible light and partially below those of x-rays Carries more energy than visible light Waves can damage skin and eyes (cause sunburn) Used to: sterilize medical equipment, kill harmful bacteria, produce vitamin D, treat skin problems and other medical conditions X-rays Very high frequencies and energy Produced by sun and stars Pass through soft tissue but is absorbed in dense matter, like bones Over exposure to x-rays can cause cancer Lead can block these types of EM waves Gamma Rays Highest frequencies and energy of all the EM waves Produced by sun and stars and some radioactive substances Gamma rays kill normal cells and cause cancer cells to develop However, doctors can use gamma rays to kill cancer cells and fight tumors when carefully c