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 radiographic exposure with 3700 GBq (100 Ci) source of Ir-192 using

1.	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)
Answer» D. 0.236 Gy/h (23.6 R/h)