https://phys.libretexts.org/TextBooks_and_TextMaps/University_Physics/Book%3A_University_Physics_(OpenStax)/Map%3A_University_Physics_II_-_Thermodynamics%2C_Electricity%2C_and_Magnetism_(OpenStax)/16%3A_Electromagnetic_Waves/16.5%3A_The_Electromagnetic_Spectrum
Waves •A disturbance that travels through space and matter •Transfers energy, not matter •Travel through electrical and magnetic fields Examples: light, microwaves, radio waves, and X-rays. Crest •The highest point on a wave is called the crest. Trough •The lowest point on a wave is called the trough. Wavelength •The distance between successive crests or troughs •Measures one complete wave Amplitude •The maximum extent of a wave measured from the position of equilibrium Frequency •The number of crests of a wave that move past a given point in a given unit of time •Measured in Hertz (Hz) Radio Waves •Longest wavelength •Lowest frequency •Coolest temperature •Examples: FM/AM radio stations, stars Microwaves •Need close proximity to transmitter •Examples: microwaves, routers, cell phones, stars Infrared Waves •“Infra” means below •These waves are just below visible light •Examples: remote controls, flames, lamps, stars Visible Light •All visible light •ROYGBIV •Examples: light bulbs, fire, stars Ultraviolet Light •Often called “black light” •Examples: sterilization, stars (sunburn anyone?), haunted houses X-Ray •High frequency waves •Examples: see inside organisms, airport security, dentist office, stars Gamma Rays •Highest frequency waves •Highest temperature (blue) •Examples: radiation therapy (cancer), sterilization, stars Studying the Universe •Astronomers use all kinds electromagnetic waves to study the characteristics (temperature, energy, color) of stars. •They can also use the EMS to determine chemical composition. Spectroscopy •A measurement technique which allows astronomers to see light that is absorbed, emitted, or scattered by materials •How do we know what stars are made out of? Star Composition •Use the class set of absorption spectrums to determine which elements are present in each star. https://www.pbs.org/video/nova-the-electromagnetic-spectrum/ Parallax •Astronomers can measure the distance of stars using a method called parallax. •They measure the star twice per year. •Every 6 months the Earth has moved nearly 186 million miles from it’s previous point due to its revolution around the Sun. Comments are closed.
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Erik E. Mason
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