[2][3] Dr. Adam Mann is experimenting with uranium-235 in the aftermath of the first atomic bomb being used in Hiroshima.
[4] During the experiment he finds himself being subjected to a strange side effect which changes his body.
These superpowers of his included the ability to see radiations which were previously invisible to normal humans.
[5] His right hand also now also emitted a large amount of Gamma radiation which allowed him to perform a number of superhuman deeds like punching through brick walls using energy blasts and controlling the minds of other people.
Knowing that the element that had given him his powers could and would be used by others for evil he took the identity of Atomic-Man and dedicated himself to fighting those who might who would try to pervert its use, along with any other criminals, mad scientists or communists who fell under the glow of his right hand.