The Doppler effect says that the observed wavelength is shortened
when the source is approaching the observer, and lengthened when
the source is receding from the observer.
All we can say about the police car and its siren is that the sound/color
has a shorter wavelength as it approaches us, and a longer wavelength
as it recedes.
Any of these pairs of answers would say that:
A -- A
C -- A
D -- A
or
D -- D
For each of these pairs, the second wavelength is longer than the first one.
(We don't know which pair is the actual one, because we don't know the actual color of the police car.)
If we relate the Doppler effect on sound to the color of light waves, a police car would be the color blue as it approaches and the color red as it recedes away from the observer.
The Doppler effect is a phenomenon that occurs when two objects move closer or farther apart, increasing (or decreasing) the frequency of sound, light, or other waves.
The Doppler effect is to sound waves as well for the light waves
The apparent shift in the frequency of the light that the observer perceives as a result of relative motion between the source of the light and the observer is known as the Doppler effect of light.
However, the equations for the Doppler shift for sound waves vary significantly depending on whether the source, the observer, or the air is moving. Light doesn't need a medium to travel, and the observer and source's relative speeds are the only factors affecting the Doppler shift for light.
A police car would appear blue as it approaches as there is an increase in frequency resulting in the decrease in the wavelength of light known as the blue shift.
similarly, it appears red as it moves away from the observer because of the decrease in the frequency resulting increase in the wavelength of the light known as the redshift.
Thus, If the Doppler effect on sound may be compared to the color of light waves, then a police car would appear blue as it approaches and red as it moves away from the observer.
Learn more about the Doppler effect from here
https://brainly.com/question/15318474
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