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The Doppler Shift The Visible Spectrum White light splits into the colors of the rainbow when passed through a prism. The Visible Spectrum Red Orange Yellow Green Blue Indigo Violet The Visible Spectrum R O Y G B I V I would like to introduce... RO Y G BIV Sometimes it gets reversed... RO Y G BIV Sometimes it gets reversed... RO Y G BIV Sometimes it gets reversed... VI B G YOR (Roy’s evil twin brother.) But the order makes no difference. There’s more to the spectrum than what you can see. Ultraviolet (UV) There’s more to the spectrum than what you can see. Pure White Light Glowing Gas The “fingerprint” of an element. Neon Light Glowing Gas Hydrogen Light When sound is made by a stationary object, you hear a certain frequency... Insert constant sound here If you could see it, it would look like this... But when the sound moves towards you, it sounds higher in pitch. Waves get compressed. The faster the object moves, the higher the pitch. Waves get compressed more. When the object moves at the speed of sound, the waves overlap... ...and you get a sonic boom. Fly faster than sound, and you’re gone before the boom is heard. Fly faster than sound, and you’re gone before the boom is heard. Fly faster than sound, and you’re gone before the boom is heard. An on-line visualization: • http://www.phy.ntnu.edu.tw/java/Doppler /Doppler.html When the sound moves away, it sounds lower. Waves are stretched. What it Sounds Like. Car 1 Deep Jet Mortor Bike 1 Prop2 Prop2 Prop 1 Race1 Race1 Whine Jet 1 Race2 Race2 The same shifting happens with the light from a moving star. Lower Frequency Higher Frequency The spectrum of hydrogen that is from a stationary source. When the star is moving closer... Stationary Hydrogen “Blue Shifted” Hydrogen from star moving towards Earth. And when a star moves away from us... Stationary Hydrogen Lines are shifted to the red end. And when a star moves away from Faster us... Stationary Hydrogen Lines are shifted farther to the red end. Since the universe is expanding... • All distant objects have a red shift. • The farther the object, the more extreme the red shift. Astronomers use this relationship between distance and speed to measure the distance to distant stars and galaxies.
