ASTR 3 Chapter 2-4: Astronomy 3 Textbook 2.4 Notes
Document Summary
As train passes by you, its train whistle changes from high shrill to low blare. This change is called the doppler effect. This is because the sound is changing frequency as it passes by you. A wave is moving from place where it"s generated toward an unmoving observer. As wave source begins to move, wave crests in direction of motion are closer together than normal, while crests behind source are more widely spread. So, observer in front of source measures shorter wavelength, while behind measures shorter wavelength. Greater relatvie speed of source and observer, greater observed shit. Apparent wavelength / true weavelength = true frequency / apparent frequency = 1 + recession velocity / wave speed. Recession velocity: positive means source and observer are moving apart. Negative value of recession velocity means they are approaching, positive means they are receeding. Wave speed is speed of light, so recession velocity normally very small.
