Modern physics Flashcards
Thermionic emission
the release of electrons from the surface of a hot metal
Cathode rays
streams of high-speed electrons moving from the cathode to the anode in an evacuated tube
photoelectric effect
The release of electrons from the surface of a metal when EM radiation of a suitable frequency falls on it
Photon
A discrete packet of electromagnetic energy. Its energy depends on its frequency.
E=hf
X-rays
High frequency electromagnetic radiation which are produced when high speed electrons strike a metal target of high melting point
An emission spectrum
Produced when light from a luminous source undergoes dispersion
Isotopes
atoms that have the same atomic number but different mass numbers due to a different number of neutrons in the nucleus
Radioactivity
The decay of a nucleus with the spontaneous emission of radiation
Three forms of radiation
Alpha
Beta
Gamma
Ionisation
the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons
Activity (A)
The number of nuclei decaying per second
Law of radioactive decay
The activity of a sample is directly proportional to the amount present
Nuclear fission
The splitting of a large nucleus into two smaller nuclei of roughly the same mass with the release of energy
Nuclear fusion
The joining of two smaller nuclei to form a large nucleus with the release of energy
Properties of an electron
Negatively charged
orbits the nucleus
very small compared to proton/neutron
Properties of cathode rays
Travel in straight lines
Cause certain substances to fluorescence
produce x-rays
deflected by electric & magnetic fields
Photocell
A device that conducts electric current when light of a suitable frequency shines on it
Geiger-Muller tube
A device used to detect radiation
