Answer:
Explanation:
The Doppler effect formula for an observer approaching a source is given by equation (1);
where is the frequency perceived by the observer, v is the actual velocity of the wave in air, is the velocity of the observer, is the velocity of the source and is the actual frequency of the wave.
The actual velocity v of light in air is . The relationship between velocity, frequency and wavelength is given by equation (2);
therefore;
We therefore use equation (3) to find the actual frequency of light emitted and the frequency perceived by Slick Willy.
Actual wavelength of light emitted is 678nm, hence actual frequency is
given by;
Also, the frequency perceived by Slick Willy is given thus;
The velocity of the source light is zero since the traffic light was stationary. Substituting all parameters into equation (1), we obtain the following;
We then simplify further to get
cancels out from both sides, so we obtain the following;
Hence;