4. With reckless disregard for safety and the law, you set your high-performance rocket cycle on course to streak through an intersection at top speed. Approaching the inter- section, you observe green (540 nm) light coming from the traffic signal. After passing through, you look back to observe red (650 nm) light. Actually, the traffic signal never changed its color when you passed itit didn't have time! (Note: you are supposed to assume here that this traffic light sends out its light waves with the same wavelength in all directions, so that you can observe those light waves both before and after you passed the intersection with your rocket cycle.) (a) What is the top speed of your rocket cycle? (b) What was the color of the traffic signal (according to an appalled bystander)?