What does the wavelength of light tell us about an objects movement?

Answer 1

Assuming the object's moving rapidly enough to affect the light from it observedly:

If approaching the light will be biased to blue (higher-f, lower wavelength);

If receding, the light will be redder (red-shift), or lower-f, longer wavelength)

by Doppler effect. If the true spectrum can be determined then the shift either way can be used to calculate the object's speed relative to the observer (not necessarily its true speed!).

Answer 2

The wavelength of light does not provide direct information about an object's movement. Rather, it is related to the color or frequency of the light emitted or reflected by the object. Doppler shift can be used to detect the motion of an object, where a change in wavelength due to the object's movement can indicate whether it is moving towards or away from the observer.