question_answer

Radium \[^{226}Ra,\] spontaneously decays to radon with the emission of an \[\alpha -\]particle and a \[\gamma \] ray. If the speed of the \[\alpha \] particle upon emission from an initially stationary radium nucleus is \[1.5\times {{10}^{7}}m/s,\] what is the recoil speed of the resultant radon nucleus? Assume the momentum of \[\gamma \]ray is negligible compared to that of \[\alpha \]particle.

A)  \[1.6\times {{10}^{4}}m/s\]

B)  \[2.7\times {{10}^{5}}m/s\]

C)  \[1.3\times {{10}^{6}}m/s\]

D)  \[2.6\times {{10}^{3}}m/s\]