Atom bomb

Atom Bomb

The  principle of fission is made use of in the construction of the atom bomb. As atom bomb consists essentially of two pieces of ₉₂U²³⁵ (or ₉₂Pu²³⁹) each smaller than the critical size and a source of neutrons. The subcritical masses of U²³⁵ in the form of hemispheres are kept apart by using a separator aperture (Fig 1).

Fig 1 

 

When the bomb has to be exploded. A third well fitting cylinder of  U²³⁵ ( whose mass is also less then critical mass) is propelled so that it will fit in or fuse together with the other two pieces. Now the total quantity of U²³⁵ is greater than the critical mass. Hence an uncontrolled chain reaction takes place resulting in a terrific explosion.

The explosion of an atom bomb releases tremendously large quantity of energy in the form of heat, light and radiation. A temperature of millions of degrees and a pressure of millions of atmospheres are produced. Such explosions produce shock wave, They are every dangerous because the waves spread radioactivity in air and cause loss of life. 

The release of dangerously radio active γ-rays, neutrons and radioactive materials presents a health hazard over the surroundings for a long time. 

The radioactive fragments and isotopes formed out of explosion adhere to dust particles thrown into space and fall back to earth causing a radiation “fall-out”, even at very distant places.