A police officer parked at the curb turns on his lights and siren, waits for traffic to clear, then pulls out and heads down the street. For an observer down the street, which is true? A. The frequency of the siren is higher and the wavelength is shorter than it was at first.
B. The wavelength of the siren is shorter than it was at first, but the frequency is the same.
C. The wavelength of the siren is shorter and the frequency is lower than it was at first.
D. The frequency of the siren is higher than it was at first, but the wavelength is the same.