Aburst of green light (wavelength 550 nm) has a total energy of 5.50 ×10–17 j. how many photons does it contain? report your answer with three significant figures. do not include units in your answer. use the format 2.22e2 or 2.22e-2 for scientific notation.

Suppose that 3% of all athletes are using the endurance-enhancing hormone epo (you should be able to simply compute the percentage of all athletes that are not using epo). for our purposes, a “positive” test result is one that indicates presence of epo in an athlete’s bloodstream. the probability of a positive result, given the presence of epo is .99. the probability of a negative result, when epo is not present, is .90. what is the probability that a randomly selected athlete tests positive for epo? 0.0297