ch. 28 Flashcards
what are x rays
they are electromagnetic waves with short wavelengths
how does x-ray diffraction work
the planes in an atoms crystalline lattice act as slits with a spacing d between them that allows diffraction to occur
when will x rays reflect from a crystal
when the angle of incidence satisfies the Bragg condition
what is the photoelectric effect
it is the emission of electrons from a substance due to light striking its surface
under what conditions do electrons emit when light strikes a surface
when the light frequency exceeds the threshold frequency f0
what happens when more intense light shines on a surface
the current increases as well
does current flow if f<f0
no, it must be greater than the threshold frequency
how does the stopping potential vary for intense and weak light
it does not, it is the same
what is the minimum energy required to release an electron from a metal called?
it is called the work function
what does measuring Vstop tell us
it tells us the maximum kinetic energy of the electrons
what is a quantum of light referred to as? what is it proportional to?
a photon, it is proportional to the frequency of the light source
what are einsteins three postulates
1.) light of frequency f consists of discrete quanta that travel at the speed of light
2.) light quanta are absorbed or emitted as whole number integers
3.) a light quantum, when absorbed by a metal, delivers its entire energy to one electron
how much energy does a photon give to an electron
all of it
how does more intense light affect the amount of electrons emitted?
it delivers more photons to the surface which, if their frequency is sufficient, will increase the amount of electrons emitted
what type of behavior do photons have
sometimes they have wave-like behavior and sometimes they have particle like behavior
