HW5_Doppler -...

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1.    The period of rotation of the sun at its equator is about 24.7 days; its radius  is 7 x 10 5  km. What Doppler wavelength shift is expected for light with  wavelength 550 nm emitted from the edge of the sun’s disk? Start with the Doppler shift formula for wavelengths, Where  λ o  is the stationary wavelength (550 nm in this problem) and Δ = - λ λ λ o  is  the Doppler wavelength shift. If it takes 24.7 days for the sun to rotate once (2Pi  x r) in the equator, then the tangential speed at the equator is: Where the days had to be converted into seconds. Solving for Δ  and using the λ   speed of light c=300,000 km/s we find: A very small Doppler shift. Better look for sun spots in motion! 2.         Use the read-outs of the frequency spectrograph in the Key Concepts  section to predict the speed at which the rotating sound source used in the data. Start with the Doppler shift formula: Where we have set v o =0 because the observer (spectrograph) is not moving.  Also notice that we will take the positive sign when the source is receding  because the observed frequency should be smaller and the negative sign when  the source is approaching because the frequency should be higher. To make things easier, let us use the numbers in red and note that there are 10 
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This note was uploaded on 10/25/2009 for the course PHYSICS Astronomy taught by Professor Me during the Spring '09 term at Akademia Ekonomiczna w Krakowie.

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HW5_Doppler -...

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