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Download The Electro-Magnetic Spectrum - EHS
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The Electro-Magnetic Spectrum Light Properties Have properties of waves… •Crests & troughs •Reflect & refract (bend) …and particles •Can travel through space EM Waves The Speed of Light = c = 3 x 108 m/s (1.9 miles/second) Travels around the world about 8 times in one second c= = frequency & = wavelength Frequency = Hertz (Hz)=1/ second Wavelength is a length – m to nm EM Spectrum Spectrum means “a range” EM spectrum ranges from long wavelengths to short Wavelength and Frequency www.nasa.go Wavelength is the distance between two peaks (or troughs) Frequency is how frequently the waves occur A longer wavelength means a lower frequency A shorter wavelength means a higher frequency Energy Frequency As frequency decreases, energy increases E = h • h = 6.626 x 10-34 Joules *second Higher energy = high frequency = short wavelength!! Energ y Light as a Particle Light = photons Photons are considered to be both particle and a wave What does that mean? • A photon is a “wave packet” • A photon is a “light particle” The Visible Spectrum red 620-750 nm orange 590-620 nm yellow 570-590 nm green 495-570 nm blue 450-495 nm indigo 420-450 nm violet 380-420 nm Visible Light Not all animals see the same wavelengths as humans Some see shorter wavelengths (ultraviolet) • Hummingbirds • Bees Others see longer wavelengths (infrared) • Bats • Snakes Visible Light vs. UV Flower in visible light Flower in UV light Visible Light vs. Infrared Bats in infrared light Bats in visible light Full Visible Spectrum Red Orange Yellow Green Blue Violet (Indigo) What does this have to do with Astronomy?? Two Girls in the IR Is this in “true color?” http://en.wikipedia.org/wiki/Infrared How do we know what a star is made of?? By looking at its EM spectrum The star’s “fingerprint” Hydrogen How light or electromagnetic radiation is used in Astronomy • Astronomers use spectroscopes • separate starlight into its colors • Identify star’s composition, temperature, luminosity • Different wavelengths provide different information • Temperature – Blackbody Radiation • Composition – Absorption Spectrum • Luminosity/Brightness Emission Spectra Full spectrum Wavelengths: H Models of a Hydrogen Atom PhET's Model of a Hydrogen Atom
