Q.4. The nuclear reaction n+510B37Li+24He is observed to occur when very slow-moving neutrons strike boron atoms at rest. For a particular reaction, the outgoing helium is observed to have a speed of 9.3106m/s. Determine a) the kinetic energy of the lithium in MeV. b) the total energy released by the reaction in MeV. Q.5. Lead (density 11.34g/cm3 ) and concrete (density 2.4g/cm3 ) are highly effective materias in radiation shielding. a) What thickness of lead in cm is required to reduce the intensity of a 0.2MeV gamma ray beam by a factor of 1000 . b) What is the thickness of concrete in cm equivalent to that thickness of lead