atomic bomb vs hydrogen bomb

atomic bomb

noun
  • A nuclear weapon that obtains its destructive energy from nuclear fission. 

  • The possession of one or more atomic bombs; the ability to launch a nuclear attack. 

hydrogen bomb

noun
  • A thermonuclear bomb that derives its destructive power from the fusion of isotopes of hydrogen (deuterium and tritium). 

How often have the words atomic bomb and hydrogen bomb occurred in a corpus of books? (source: Google Ngram Viewer )