Quantum Physics Flashcards
What is meant by de Broglie wavelength
wavelength of wave associated with a particle that is moving
What is meant by the threshold frequency
minimum frequency for the electron of electromagnetic radiation/ light/ photons to be emitted from surface
Evidences provided by the photoelectric effect for a particular nature of electromagnetic radiation
-‘instantaneous’ emission of electrons
-threshold frequency below which no emission
-max electron energy dependant on frequency
-max electron energy not dependant on intensity
-rate of emission of electrons depends on intensity
Describe the concept of a photon
‘packet’/ quantum of energy
of electromagnetic energy/ radiation
What is meant by work function of the surface
-energy of photon to cause emission of electron from surface either with zero KE or photon energy is minimum
or
-energy of photon required to remove electron from a surface
Why most of the emitted electrons will have a speed lower than Vmax
-electrons are liberated from atoms at different depth
-energy is lost as electron move to surface/ energy is required to bring electron to the surface
The spectrum of the light emerging from the gas cloud is found to contain a number of dark lines
Explain why these dark line occur
-photon ‘absorbed’ by electron
-photon has energy equal to difference in energy of 2 energy levels
-electron de-excites emitting photon of the same energy in any direction
Use band theory to explain why the resistance of an intrinsic semiconductor decreases as its temperature rises
-as temperature rises, energy of electrons increases
-electrons have enough energy to cross forbidden band
-electrons enter conduction band
-leaving hole in valence band
-both holes and electrons act as charge carriers
-more charge carriers results in lower resistance
-increased lattice vibrations outweighed by increase in number of charge carriers
