13.1 - 13.4 Flashcards
what is a photon
a quantum (packet) of energy. a particle of light
how is the energy of a photon linked to its wavelength
energy is inversely proportional to the wavelength
what is the electronvolt
a unit of energy used when dealing with very small amounts of Joules. It’s the energy transferred by one electron when it passes through a potential difference of one volt
how can Planck’s constant be determined
using LED’s which emit a known wavelength of light. find the threshold potential difference then calculate h using h= eV/f
whats the photoelectric effect
the emission of surface electrons from a metal when EM radiation above the threshold frequency is incident on it
3 key observations about the photoelectric effect
if the frequency was too low not a single electron would be emitted
if the frequency was sufficient the emission of electrons was instantaneous
increasing intensity only increases the number of electrons released. not affecting their maximum kinetic energy
why can the wave model not explain the photoelectric effect
in the wave model, the rate of transfer of energy is dependent on its intensity. this fails to explain why increasing intensity doesn’t increase the energy of the photoelectrons
how does the photon model explain the photoelectric effect
each photon transfers all of its energy to one electron each. since E=hf if the frequency is too low there is insufficient energy to cause the photoelectric effect. intensity is the number of photons arriving per second but each electron absorbs the energy of one photon so it has no effect on the maximum kinetic energy.
what is the work function
the minimum energy required to remove a surface electron from a particular metal
what is the wave-particle duality
all matter behaves as both a wave and a particle. de Broglie realised all matter travels through space as a wave. anything with mass that is moving has wave-like properties
why is the wave property of large particles hard to observe
larger particles have a greater mass so their momentum at the same speed is greater than smaller ones. this causes a smaller de Broglie wavelength which is much harder to observe.
