Work out shielding half value layer instantly with clear inputs, formula shown and shareable results.
Shielding follows exponential attenuation, I = I0 exp(-mu.x), so the half-value layer is ln2/mu. With mu = 0.7 per cm the HVL is 0.99 cm, and 5 cm of shield is just over five HVLs, cutting the beam to 3% - an attenuation factor of 33. Exponential decay means there is no thickness that stops radiation completely.
Exponential attenuation
I = I0 exp(-mu x)
Half-value layer
HVL = ln2 / mu
Because attenuation is exponential - each layer removes a fixed fraction, not a fixed amount. Practical shielding aims for an acceptable dose rate, not zero.
About 12 mm for cobalt-60 gammas at 1.25 MeV, and only 0.1 mm for diagnostic X-rays, which is why thin lead aprons work.