## College Physics (4th Edition)

(a) The observed frequency is $1.5~kHz$ (b) The observed frequency is $500~Hz$
(a) We can use the equation for the Doppler effect when the observer is approaching: $f_o = \left(\frac{v+v_o}{v}\right)~f_s$ $f_o = \left(\frac{v+v/2}{v}\right)~f_s$ $f_o = \left(\frac{3}{2}\right)~f_s$ $f_o = \left(\frac{3}{2}\right)~(1.0~kHZ)$ $f_o = 1.5~kHz$ The observed frequency is $1.5~kHz$ (b) We can use the equation for the Doppler effect when the observer is moving away: $f_o = \left(\frac{v-v_o}{v}\right)~f_s$ $f_o = \left(\frac{v-v/2}{v}\right)~f_s$ $f_o = \left(\frac{1}{2}\right)~f_s$ $f_o = \left(\frac{1}{2}\right)~(1000~Hz)$ $f_o = 500~Hz$ The observed frequency is $500~Hz$