(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A proton (1.6726×10-27 kg) and a neutron (1.6749×10-27 kg) at rest combine to form a deuteron, the nucleus of deuterium or "heavy hydrogen". In this process, a gamma ray (high-energy photon) is emitted, and its energy is measured to be 2.39 MeV (2.39×106 eV). Keeping all five significant figures, what is the mass of the deuteron? (Assume you can neglect the small kinetic energy of the recoiling deuteron.)

2. Relevant equations

Rest Energy = m c^2

E_{before}=E_{after}

3. The attempt at a solution

I found the energy before the combining by

c^2 (1.6726×10-27+1.6749×10-27) = 3.0086*10^-10 J

this should equal the energy of the deuteron (mc^2) + the energy of the photon

energy of the photon in joules: 3.8292*10^-13 J

therefore:

3.0086*10^-10 = m_{d}c^2 + 3.8292*10^-13

m_{d}=3.3433*10^-27 kg

However, this isn't right

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# Homework Help: Energy of a deuteron

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