How is the transmission factor through shielding quantified?

• A. B = I0 / I = e^{μx}
• B. B = I / I0 = e^{μx}
• C. B = I / I0 = e^{-μx}, with μ the linear attenuation coefficient and x the thickness
• D. B = I0 - I = μx

Answer: (C)

Attenuation through shielding follows an exponential decay: the beam’s transmitted intensity I is reduced from the incident intensity I0 according to I = I0 e^{-μ x}, where μ is the linear attenuation coefficient of the shielding material and x is the thickness the beam travels through. The transmission factor is the ratio of transmitted to incident intensity, B = I / I0, which gives B = e^{-μ x}. This form correctly shows how thicker shielding or a material with a larger μ reduces the transmitted beam.

The other forms aren’t correct because they either suggest linear change (I0 − I) or an increasing intensity with thickness (e^{μ x} or I / I0 = e^{μ x}), which contradict the physics of exponential attenuation.