Lect14 - Lecture 14: Light Spectral Lines Doppler Effect...

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1 Lecture 14: Light Doppler Effect for Light ReFection Refraction (Snell ʼ s Law) Total Internal ReFection ±iber Optics Dispersion Rainbow Prizms October 11 Physics 104, Fal 2011 Spectral Lines Astronomers use spectral lines to determine proper1es of stars Each dark line in the spectrum corresponds to a color absorbed by the atoms in the object The loca1on of each line corresponds to a par1cular wavelength of light Some spectra are observed to be shi>ed Section Doppler Effect and EM Waves A Doppler Effect occurs for em waves , but differs from that of sound waves – For sound waves, motion relative to a medium is most important • For light waves, the medium plays no role since the light waves do not require a medium for propagation – The speed of sound depends on its frame of reference • The speed of em waves is the same in all coordinate systems that are at rest or moving with a constant velocity with respect to each other October 11 Physics 104, Fal 2009 3 Doppler Equation for EM Waves The Doppler effect for em waves f’ is the observed frequency f is the frequency emitted by the source u is the relative speed between the source and the observer – The equation is valid only when u << c October 11 Physics 104, Fal 2009 4 f ' = f 1 ± u c Λ Ν Μ Ξ Π Ο Doppler Equation • The positive sign is used when the object and source are moving toward each other • The negative sign is used when the object and
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This note was uploaded on 11/30/2011 for the course PHYSICS 104 taught by Professor Dasu/karle during the Fall '11 term at Wisconsin.

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Lect14 - Lecture 14: Light Spectral Lines Doppler Effect...

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