Doppler Effect for Light
can we use the same result for light by replacing v by c ? c=3.00 x 108 m/s
f `= f ( 1 ± u/c) higher if approaching! u<<c
in astronomy we measure wavelengths
(? `- ?)/ ? ~ u/c Doppler shift
decrease => blue shift => f ` increase=>approach
increase => red shift => f ` decrease => receding
light from all distant galaxies is red shifted