Christian Doppler Discovered What We Now Call the "Doppler Effect

Multiple Choice

Christian Doppler discovered what we now call the "Doppler Effect" by measuring:

A) the wavelengths of the Balmer lines of hydrogen
B) the intensity of the red and blue light from the same star
C) the changes in the radar gun used by his local police officers when they pointed at speeding cars
D) the changes in the colors of a rainbow when the clouds were moving fast
E) the properties of sound waves coming from a group of musicians on a moving, open railroad car