7A.2 Electrons from atoms Flashcards
what is the photoelectric effect
when electrons are released form a metals surface because the metal is eat by a EM radiation
what is thermionic emission
the release of electrons from the surface of a metal caused by the heating of the metal
the Kinetic energy that the electrons experience in an electric field depend on
the p.d they move through linked by this equation Ek = eV
what is a cathode ray
a beam of electrons
how can we form a beam of electrons
by using thermionic emission of the photoelectric affect to produce electrons then use and electric field to accelerate them
if a cathode ray passes through a further electric/magnetic field what will happen
the force on the ray would cause it to deflect
if fast moving electrons hit a screen that is painted with a particular chemical what will happen
the screen will fluoresce. it will emit light
why are CRO (cathode ray oscilloscopes) useful
because they can change the direction of the ray easily by passing the beam through a vertical and horizontal electric field, and because the power of the beam can be altered since its made by electric plates
how can we tell the structure of a crystal using electrons
by firing an electron beam onto a crystal in will form a scattering pattern which will tell us about the structure
what is the De Broglie wavelength
landa = h/p
how did shooting electron beans at crystals prove the De Broglie wavelength
when the electron beam was shoot at the crystal it created a diffraction pattern which only can be occur if the beam had a wavelength
so how can we observe electron diffraction
by measuring the radius of a circular pattern for every accelerating voltage then you can preform calculations to find the De Broglie wavelength
when a wave passes through a gap that is the same size as there wave length what will happen
they will diffract
the degree of diffraction of a wave depends on
the ratio of the size of the gap compared to the wavelength of a wave
how are electrons diffracted when shoot at crystals
the gaps between the crystals can act as a diffraction grating, with a diffraction pattern formed in which we can calculate the distance between the atoms
