Dose is the deposited-energy ledger divided by the mass that received it. The worked rows compare 12 joules in 3 kilograms, which gives 4 joules per kilogram, with a shielded case of 3 joules in the same mass, which gives 1 joule per kilogram. Real dose estimates depend on detector calibration, absorbed fraction, material geometry, mass measurement, time variation, and uncertainty.
Dose is a physics ledger: deposited energy divided by mass. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Dose is deposited energy per mass
Before shielding, 12 joules deposited in 3 kilograms gives 4 joules per kilogram.
12÷3=4J/kg
Shielding changes the deposited energy ledger
After shielding, 3 joules in the same 3 kilograms gives 1 joule per kilogram.
3÷3=1J/kg
The final audit cites checked nuclear sources
The audit joins isotope, decay, half-life, binding, attenuation, and dose ledgers with accepted bit 1.