Third and final A2 Physics paper tomorrow. Currently struggling with one of the articles we have been given to study before the exam. It's all about neutrinos. I've been given some questions to try, educated guesses by teachers on what could come up on the exam paper. "If the Sun is 150 Gm away and produces 2 * 10^38 (2E38) neutrinos per second, what is the neutrino flux density at the earth's surface?" My best guess based on what I know about magnetic flux density so far is: 2E38 / 150G = 1.3E27 I realise that 150Gm isn't an area, but that's the best I could do! Is there anyone that can confirm my answer/tell me it's all completly wrong? Thanks.