What is the purpose of the transmission factor in shielding design and how is it computed?

• A. Transmission factor indicates the fraction of beam absorbed by shielding.
• B. Transmission factor is defined as the ratio of transmitted to incident beam, but it is not used in shielding calculations.
• C. Transmission factor indicates the fraction of beam transmitted after shielding; computed by T = I_transmitted / I_incident, often via e^{-μx} or HVL-based methods.
• D. Transmission factor is only used in evaluation of image quality and has no shielding relevance.

Answer: (C)