Answer
$D = 0.0025 \space Sv= 2.5 \space mSv$
Work Step by Step
To find the absorbed dose, energy in joule is divided by mass of subject.
Absorbed dose, $D = \frac{E}{m}$
$D = \frac{2.0 \times 10^{-3} J }{4.0 kg}$
$D = 5.00 \times 10^{-4} J/kg$
*Note that 1 J/kg = 1 Gy
$D = 5.00 \times 10^{-4} Gy$
To find the answer in Sv, The dose of $5.00 \times 10^{-4} Gy$ must be multiplied by the relative biological effectiveness, $RBE = 5$
$D = (5.00 \times 10^{-4} Gy)(5)$
$D = 0.0025 \space Sv= 2.5 \space mSv$
