Question

Because of the Doppler effect, wavelengths of light _______ as the source moves toward an observer and _______ as the source moves away.
A.
shorten (blueshift); lengthen (redshift)
B.
lengthen (redshift); shorten (blueshift)
C.
lengthen (blueshift); shorten (redshift)
D.
shorten (redshift); lengthen (blueshift)

Answer 1

A. shorten (blueshift); lengthen (redshift)

When a light source moves toward an observer, the wavelengths are compressed (blueshift); when it moves away, they are stretched (redshift).