Q. The half value layer of lead for Co-60 is approximately 13 mm (0.5 in). If the radiation level on the source side of a 38 mm (1.5 in) lead plate is 0.64 Gy/h (64 R/h):, the radiation level on the opposite side is:

• (A) 0.08 Gy/h (8 R/h).
• (B) 0.213 Gy/h (21.33 R/h).
• (C) 0.107 Gy/h (10.67R/h).
• (D) 0.32 Gy/h (32 R/h).