unit 2. calculations Flashcards
how to calculate binding energy if the velocity of the ejected electron is given and light frequency
- calculate energy of photon E=hv (make sure units of frequency is correct)
2.Ekinetic= 1/2mv2 (since. binding is threshold, we know there is kinetic energy, so we use this)
to get binding energy we use KE=hv-hvo
(photon energy-binding number)
since we have both kinetic energy and energy of photon
finally, if asked in per mol, multiply by avagrados number.
energy of photon formula units are..
joules per photon.
if we want per mol, multiply by avagrado’s number
if we are finding the energy of photon units needs to be…
kj/photon
or j/photon
formula if the wavelength of light or source (x-ray) given, what is the frequency
use C= (wavelength)(frequency)
rearrange to get the frequency
beam of light with energy= 6.4E-19
on gold surface with energy of 6.4E-19. what is the maximum kinetic energy
we dont even need to use kinetic energy formula since the hv (energy of light/photon) is less than hvo (threshold frequency).
remember we can only calculate kinetic energy if we have electrons ejected.
questions asking “is there a sufficient energy in a single photon of light to eject an electron
we use energy formula either E=HV or the one that has wavelength.
now check if result is bigger than hvo (binding energy)
if answer is yes, calculate KE
when total energy of light given and asking for number of phtons pulse contains, wavelength given
E total/ Ephoton
since total already given, we find energy of one photon by using energy of photon formula
calculating energy if energy levels are given
use EN= -2.18*10E15/ nE2
additionally, if it also ask for wavelength, we already hav energy and we can use energy formula with wavelength, rearrange it and it.
find wavelength of electron with speed of given
we use lambda = h/mv
