1. The problem statement, all variables and given/known data You are cruising to Jupiter at the posted speed limit of 0.1c when suddenly a daredevil passes you, going in the same direction, at 0.3c. At what wavelength does your rocket cruiser's light detecter "see" his red tail lights? Is this wavelength ultraviolet, visible, or infrared? Use 650 nm for the wavelength of red light. 2. Relevant equations I used the dropper effect for the light of a receding source" √((1+vs/c)/(1-vs/c) * λo 3. The attempt at a solution I tried using 0.3c for the speed of the source, and 650 for λo. (I know the answer is 800 nm); I then tried using 0.1c instead. I got (almost) the right answer though when I plug in 0.2c... the wavelength came up as 796 nm. Don't know what else to use!