Theory of Relativity, he showed that light waves would have Doppler
shifts that would exactly, not just approximately, depend only on
the relative motion of the source and receiver.
Discussion Questions
A If an airplane travels at exactly the speed of sound, what would be
the wavelength of the forward-emitted part of the sound waves it emitted?
How should this be interpreted, and what would actually happen? What
happens if it’s going faster than the speed of sound? Can you use this to
explain what you see in figures aa and ab?
B If bullets go slower than the speed of sound, why can a supersonic
fighter plane catch up to its own sound, but not to its own bullets?
C If someone inside a plane is talking to you, should their speech be
Doppler shifted?
Section 6.1 Free waves 373