Determine the mean penetration depth in water of the following ionizing radiatio

Question

Determine the mean penetration depth in water of the following ionizing radiation: 5 MeV alpha particles with an average LET = -1450.00 MeV/gm-cm^-2 5 MeV electrons with an average LET = -2.00 MeV/gm-cm^-2 5 MeV protons with an average LET = -420.00 MeV/gm-cm^-2 Work exercise 9.16. As discussed in textbook section 9.6.2, stopping power S and linear energy transfer LET are practically equal S dE_d/dx, eq. 9.14 ax where dE_d is energy deposited over distance dx. Depth of penetration R (also called the "range") of a particle is given by R = 1/rho integral_0^E dE/LET_rho, eq. 9.29 where LET_rho is average energy absorbed per unit path length, per unit mass density. units of [LET_rho] = energy/length Times density = J/cm g/cm^3 = J/g/cm^2 = J cm^2/g LET_rho may also be expressed in terms of MeV units of [LET_rho] = MeV/g/cm^2

Explanation / Answer

density of water = 1gm/cm3

For alpha particles, r = 1 * 5/1450 = 3.4*10^-3 cm

For electrons , r = 5/2 = 2.5 cm

For protons, r = 5/420 = 11*10^-3 cm

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