In a radioactive decay, Plutonium disintegrates to ²³⁵ U and an particle. After the disintegration the mass difference between the parent nucleus and the products of the decay is found to be 0.00536 u . The energy of the released particle is reduced while passing through a Mylar sheet with linear absorption coefficient of 1.40 ~cm ⁻¹ . If the energy of the most energetic particles is to be reduced to 2 MeV the thickn