Quantum Mechanics Flashcards
photons, energy levels, photoelectricity
what causes photoelectricity?
photons of light incident on a metal excite the surface electrons, which are then emitted
what are photons?
wave ‘packets’ of energy
what does a higher intensity mean in terms of photons?
more photons arriving per second
in a graph of the photoelectric effect (Ekmax against frequency) what is the gradient, y-intercept and x-intercept?
gradient is Planck’s constant
y-intercept is the negative work function
x-intercept is the threshold frequency
what is the work function?
minimum amount of energy needed to release an electron.
Planck’s constant x frequency
what is the threshold frequency?
minimum amount of energy needed to release an electron (same as work function)
what is the stopping potential?
what happens when it is reached?
(negative) voltage needed before no electrons can make it to the opposite plate and begins to return to the plate they came from.
when reached, the current becomes zero
what limits the amount of current that can be produced?
the amount of electrons released per second
how do fluorescent lamps emit UV photons?
How is the UV light turned into visible light?
uses electricity to excite mercury vapour, when the atoms relax, they release UV photons
converted using phosphor, which coats the inside of the bulb and fluoresces when bombarded with the UV light
