This questions contains several different parts, including: a)determining which way a star is moving by shifted wavelength of absorption lines, b)determining which way a police car is moving by measuring a shift in frequency of its siren, c)determining which way quasars move by acknowledging that they all seem to have high redshift, and d)determining based on direction of motion which speeding car would get a ticket from an officer using a radar gun.
keywords: Doppler shift, wavelength, police, siren, quasar, radar gun, ticket, redshift
swf file: ca_light_dopplershift.swf