He pp i chain can be summarised as: 4he2e* 2ve 2y 4h + + throughout this question, state clearly any assumptions that you make (i) hydrogen and helium nuclei have masses mh 6.645 x 10-27 kg respectively, and the positron has the same mass as the electron, me9.109 x 10-31 kg. calculate the energy liberated by each oc- currence of the pp i chain and hence estimate the rate at which this reaction is taking place in the sun's core. 1.673 x 10 27 kg and mhe [4] (ii) estimate the total amount of time in years for which the solar luminosity be maintained at its current value by hydrogen fusion. can [4] (ii) the positrons produced by the pp i chain will annihilate when they encounter an electron, producing two y-rays with the same energy. calculate the wave- length of these y-rays [3] (iv) estimate how many photospheric photons are needed to radiate away the energy produced by one pp i reaction, and hence how many photons are radiated by the sun each second. [2] (v) estimate how many solar neutrinos pass through your brain each second