Unless indicated otherwise, assume the speed of sound in air to be v = 344 m/s. How fast (as a percentage of light speed) would a star have to be moving so that the frequency of the light we receive from it is 10.0% higher than the frequency of the light it is emit-ting? Would it be moving away from us or toward us? (Assume it is moving either directly away from us or directly toward us.)

Solution 53E Introduction We will use the formula of doppler effect of light to calculate the speed of the star. Step 1 (a) The doppler effect in the light is given by fr= c+vfs Let us now consider that the source frequency is f . Since the frequency measured by the receiver is f is s r 10% then we have f =rf + s.1f = s.1f . s So from the above equation we have So the star would have to move with 4.8% of the speed of the light.