What is the depth of Penetration is steel by cobalt-60, Cesium-137, Iridum-192 & Thulium-170?

Ans:

Penetration is steel by:-

(A) Cobalt - 60 - 9(inch)
(B) Cesium - 137 - 3 1/2 (inch)
(C) Iridum - 192 - 3 (inch)
(D) Thulim - 170 - 1/2 (inch)