FISSION

DEFINITION: -

"The process in which a heavy nucleus is broken into two lighter nuclei with the release of energy is called Nuclear Fission."

OR 

The disintegration of a heavy nucleus after capturing neutron with 
the release of energy is called "Nuclear Fission."

In one fission of ₉₂U²³⁵ nucleus, about three neutrons are obtained. 

FISSION IN ₉₂U²³⁵

In 1939, Hann and Stressman discovered that fission can be produced by bombarding ₉₂U²³⁵ with slow neutrons. When ₉₂U²³⁵ is bombarded with neutron, it is broken down into two lighter nuclei and about 200Mev energy is released in this process.

COLLISION GEOMETRY: -

Fission reaction in uranium can be explained by the following schematic diagram.