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Modern Physics

TermDefinition
Isotope Atoms that have the same atomic number, but have different mass numbers
Atomic Number The number of protons and neutrons in the nucleus of an atom of the element
Mass Number The total number of protons and neutrons in the nucleus of an atom of the element
Thermionic Emission The emission of electrons from the surface of a hot metal
Photoelectric Emission The emission of an electron from the surface of a metal when light of the correct frequency falls on it
Threshold Frequency The minimum frequency required for photoemission to occur
Work Function The minimum energy required by a photon to remove an electron from the surface of a metal. ϕ=hf0
X-Rays High frequency photons of electromagnetic radiation that are produced when high speed electrons strike a heavy metal target
Radioactivity The decay of a nucleus of an atom with the emission of one or more of the three types of radiation
Activity The number of nuclei of a radioactive substance that are decaying per second
Becquerel The unit of activity. One becquerel is one radioactive disintegration per second
Law of Radioactive decay The number of disintegrations per second is directly proportional to the number of nuclei present. Rate of Decay = λN
Half-Life The half-life of a radioactive isotope is the time taken for half the nuclei present to decay T1/2 = ln2 / λ
Nuclear Fission The splitting of a large nucleus into two smaller nuclei with the emission of large amounts of energy
Nuclear Fusion The joining together of two light nuclei to from a larger nucleus with the emission of large amounts of energy
Popular Physics sets

 

 



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