08-HubbleRedshift - 8. Hubble Redshift PreLab Name:...

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8. Hubble Redshift – PreLab Name: Section: Date: (2) Question 1: Imagine someone is throwing tennis balls at you. They throw a ball once a second. If you run towards them would you get hit more or less often? What if you are running away from them? The Doppler Effect When objects are moving the frequency, or “pitch” of waves can change. We are all more familiar with this concept than we might think. Think of the noise a car makes when you are standing next to it, a sort of low purr. Now imagine you are standing on a highway and the same car zooms by at a high speed. It makes a vvvrrrroommm sound right? So the movement of the car does affect the sound. You've probably also noticed this effect with ambulances and emergency vehicles as they pass by. The frequency or “pitch” of sound is simply how often the waves repeat themselves. Take a look at this diagram. (Illustration thanks to Aperion University) If these waves were to slide into your ear, your brain would receive peaks and valley's faster for the top wave than for the bottom. Hence a higher pitch.
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(2) Question 2: Think about the example with tennis balls in question one. If something was emitting waves and you moved towards it would you see the waves repeat more often or less often? If it were a sound wave would it sound higher or lower? Light is a Wave Light and sound are very separate distinct phenomena. However, they are both waves. The frequency or “pitch” of light is also affected by movement. The “pitch” of light is more commonly referred to as color. When the ambulance is moving towards you the pitch or the siren is shifted higher. The red lights are also a tiny tiny bit bluer. The amount the light gets shifted is: V/c * F0 Where V is how fast the object is moving towards or away from us, c is the speed of the wave, and F0 is the original frequency of the wave. (2) Question 3: You are moving very quickly towards something that is already very blueish/violet. You notice it disappears and you can't see it anymore. Why is this? What “color” did it become? (You may want to put on some sunscreen) (2) Question 4: The speed of sound is about 340m/s. Imagine an evil trombonist launches himself out of a cannon towards a
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This note was uploaded on 02/01/2012 for the course PHYS 133 taught by Professor Staff during the Fall '08 term at University of Delaware.

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08-HubbleRedshift - 8. Hubble Redshift PreLab Name:...

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