How is shielding thickness t calculated from HVL data for a gamma source?

How is shielding thickness t calculated from HVL data for a gamma source?

• A. t = HVL × log2(I0/I)
• B. t = HVL ÷ log2(I0/I)
• C. t = I0/I × HVL
• D. t = HVL × ln(I0/I)

Answer: (A)

HVL is the thickness that reduces the gamma-ray intensity by a factor of 2, so the transmitted intensity after shielding is I = I0 × 2^(-t/HVL). Rewriting, I0/I = 2^(t/HVL). Solving for t gives t/HVL = log2(I0/I), hence t = HVL × log2(I0/I). You can also write this with natural logs as t = HVL × ln(I0/I) / ln 2. This is the correct way to extract thickness from HVL data.

HVL is the thickness that reduces the gamma-ray intensity by a factor of 2, so the transmitted intensity after shielding is I = I0 × 2^(-t/HVL). Rewriting, I0/I = 2^(t/HVL). Solving for t gives t/HVL = log2(I0/I), hence t = HVL × log2(I0/I). You can also write this with natural logs as t = HVL × ln(I0/I) / ln 2. This is the correct way to extract thickness from HVL data.