Question

Atomic bomb is based on?

Answer 1

Atom bomb is based on the principle of nuclear fission.
===============

Nuclear fission is the phenomenon where the nucleus of a heavy atom (nucleus which contains many nucleons, such as uranium and plutonium nuclei) is divided into several lighter nuclei, usually two nuclei.

Answer 2

Atomic bomb is based on the principle of Nuclear Fission.

Nuclear Fission is a nuclear reaction in which a heavy  nucleus (such as Uranium and plutonium )spilts into smaller nuclei and releases a lot of energy.

Hope it helps.