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lecture8_ch5b - Light The Cosmic Messenger How does light...

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1 Light: The Cosmic Messenger How does light tell us the speed of a distant object? The Doppler Effect Hearing the Doppler effect Cause of the Doppler effect Doppler effect for light Doppler Shifts REDSHIFT Moving AWAY Longer wavelengths “Redder” BLUESHIFT Moving TOWARD Shorter wavelengths “Bluer” No moving or moving ACROSS - No shift V=0 (or across) V>0 (away) V>>0 V<0 (towards) V<<0 Doppler Effect & Relative Motion Wavelength Measuring Redshift is Measuring Velocity
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2 Doppler Effect Summary Motion to or away from an observer causes a a shift in the observed wavelength of light. Motion towards you -> “blueshift” = shorter wavelengths. Motion away from you -> “redshift” = longer wavelengths Motion across the sky -> no shifts. Size of the wavelength shift measures speed. Telescopes How do telescopes help us learn about the Universe? Advantages over eyes Bigger (more sensitive, more accurate) Can add cameras, CCDS Can “see” more of the electromagnetic spectrum Bigger is better 1.
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