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There is one isolated atom of iron which emits K_alpha X-rays of energy 6.4 keV . With what kinetic energy, the iron atom will recoil If mass of iron atom is 9.3xx10^(-26) kg. |
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Answer» Solution :Using conservation of linear momentum we can understand that the linear momentum of iron atom MUST be equal in magnitude but opposite in direction to that of linear momentum of photon so that total linear momentum remains zero after the emission of photon because there is no external force ACTING on the system . Linear momentum of photon can be written as follows : `p=E//c=(6.4xx10^3xx1.6xx10^(-19))/(3xx10^8)=3.41xx10^(-24) kg m s^(-1)` Linear momentum of iron is also same in magnitude so its kinetic energy can be written as follows : `K=p^2/(2m)=(3.41xx10^(-24))^2/(2xx9.3xx10^(-26))=(11.63xx10^(-48))/(18.6xx10^(-26))=6.25xx10^(-23)` J `=(6.25xx10^(-23))/(1.6xx10^(-19))`EV =`3.9xx10^(-4)` eV |
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