Q. A radiographic exposure with 3700 GBq (100 Ci) source of Ir-192 using source to film distance of 60 cm results in a radiation intensity of 0.12 Gy/h (11.8 R/h) and a radiographic density of 2.5. The intensity of radiation needed to obtain the same density when the source to film distance is changed to120 cm is:

• (A) 0.472 Gy/h (47.2R/h)
• (B) 0.118 Gy/h (11.8 R/h)
• (C) 0.029 Gy/h (2.9 R/h)
• (D) 0.236 Gy/h (23.6 R/h)