Quantum phenomena Flashcards
Photoelectric effect
electrons are emitted from a surface of a metal and when electromagnetic radiation above a certain frequency was directed a the metal
Einsteins explanation of the photoelectric effect
- An electron at the surface absorbs a single photon and gains energy equal to hf
-then the electron can leave the metal surface if the energy gained is above the work function of the metal (min energy needed for the electron to escape the metal surface)
-and any extra energy gained by the photoelectron become its kinetic energy
stopping potential
min energy to stop the photoelectric emission
at this potential e k max can be reduced to 0 as the electrons have to do extra work to leave the surface
formula for ek max
planks constant x frequency + work function
More about the photoelectric effect
When a conduction electron absorbs a photon, its kinetic energy increases by an amount equal to the energy of the photon. If it is greater than the work function of the metal, then the electron can leave the metal. If it is not greater than the work function, the electron collides repeatedly with other electrons and positive ions and loses its extra kinetic energy.
Work function
minimum energy needed by a conduction electron to escape from the metal surface when the metal is at zero potential.
ground state
The lowest energy state of an atom
excitation
an electron in a shell when a photon comes in and its absorbed by the electron if the electron gets more energy then it jumps to a shell and so it goes up an energy level
ionisation
this happens when an electron is given enough energy by a photon or free electron and it jumps out of the atom completely and your left with free electron and ion
de excitation
electron returns to lower energy level ,energy is released and a photon is emitted
de broglie wavelength formula
planks constant / momentum ( Mass x velocity)
