On August 6, the “Little Boy” was dropped by the B-29 Superfortress Enola Gay on Hiroshima. It was a gun-type Uranium bomb.
“The bomb delivered its destruction in stages. The flash come from a fireball 300 m wide. Temperature immediately below the fireball, was 4000 degree celsius. Anyone in the open area was vapourised or turned to carbon in an instant. At the same time, the flash also sent out powerful infra-red and gamma rays. These could penetrate walls and attack the cells in human body. A fraction of a second later came a powerful shock wave that traveled at the speed of sound. It turned everyday windows and walls into shrapnel.”
Applet PhET Nuclear Fission: Click HERE