What is a hydrogen bomb?

A hydrogen bomb is potentially vastly more destructive than the atomic bombs that devastated the Japanese cities of Nagasaki and Hiroshima in 1945.

An H-bomb derives much of its power from the nuclear fusion of hydrogen isotopes.

Unlike an atomic bomb, which works by a fission process where uranium or plutonium is split into lighter elements, a hydrogen bomb functions by the fusing of lighter elements into heavier elements.

The end product still weighs less than its components, with the difference appearing as energy.

Hydrogen bombs are also known as thermonuclear bombs, because extremely high temperatures are needed to start fusion reactions.

An atomic bomb forms the centre of a hydrogen bomb.