# How to find how many atoms have to decay to get some amount of power? [closed]

How do I get the power when there is no charge, or anything else given in the question? Is there a power formula that I'm not aware of? Please help!

A nucleus of plutonium-238 ($$^{238}_{\ \ 94}$$Pu) decays by emitting an $$\alpha$$-particle to produce a new nucleus X and 5.6 MeV of energy. The decay is represented by $${}^{238}_{\ \ 94}\rm Pu \to X + \alpha+5.6\:MeV.$$ Calculate the number of plutonium-238 nuclei that must decay in a time of 1.0 s to produce a power of 0.15 W.

• "there is no energy given in the question" - maybe you should read the question more carefully, particularly the part that says "to produce 5.6MeV of energy". – Emilio Pisanty Mar 15 at 10:27
• On a housekeeping note, please do not post images of texts you want to quote, but type it out instead so it is readable for all users and so that it can be indexed by search engines. For formulae, use MathJax instead. – Emilio Pisanty Mar 15 at 10:30

You are told the energy released by one decay is $$5.6$$ MeV (mega electronvolts). A power of $$0.15$$ Watts is $$0.15$$ Joules per second. The only missing piece is the conversion factor between MeV and Joules.