Attenuation and half-value layer: interactive simulator

The relationship to understand

N/N₀=exp(−μx)=2^(−x/HVL), with HVL=ln(2)/μ. HVL means half-value layer, the thickness halving the uncollided beam intensity.

Try it and interpret

For a half-value layer of 2 cm and a thickness of 6 cm, the model transmits 1/8, or 12.5%. Double the thickness to distinguish exponential decay from linear subtraction.

Assumptions and limitations

Narrow monoenergetic beam, homogeneous material and constant μ. Scattering, beam hardening and real geometry can invalidate this simple model. This is not a shielding-design or clinical-dose calculation.

Go further with the course

This page focuses on one concept. The full chapter (French) contains the reasoning, further examples, slides and FAQ. Demonstration values are computed or constructed within the stated model; they are not new research findings.