Travelling towards a traffic light and doppler effect.

[Lengalicious]

To find out how fast you would have to be going in order to to see a green light when the light is infact red what doppler equation would you use. I used f = ((c+v)/c)*f₀. Is this wrong, if so why?

 

[rcgldr]

zero as long as the observer is some non-zero distance from the light, there's a delay = (speed of light) / distance, between the light changing and the observer seeing the change.

... unless you mean shifting of apparent frequency:

http://en.wikipedia.org/wiki/Redshift

http://en.wikipedia.org/wiki/Relativistic_Doppler_effect