1.3 The photoelectric effect Flashcards
What happens if a wave of a frequency lower than the work function hits the charged plate?
No photoelectrons will be emitted as there isn’t enough energy to release the electron from the metal
What kind of light is needed for the photoelectric effect to occur?
UV light
What model of light does the photoelectric effect support?
The particle nature of light
How does the intensity of light affect the emitted photoelectrons?
The rate photoelectrons are released increases proportionally as intensity of light increases
Define threshold frequency
The minimum frequency of incident light required to release electrons from the suface of the metal (cause photoelectric emission)
Define the work function
The minimum energy the surface electron requires to be removed from the metal
Define excitation
Where gas atoms absorb energy which promotes them to a higher energy level
What happens after an electron is excited
It released a photon to return it to a lower state, this can be over several levels or just one level. The electron eventually returns to its ground state where it started.
Describe excitation by electron collison
The incident electron must have sufficient kinetic energy to promote the electron to a higher energy level or else it just deflects away, any surplus energy is carried away by the incident electron.
Describe excitation by photon absorption
The incident photon must have exactly the right amount of energy to promote the electron to a higher energy level or nothing happens
Describe the emitted photons after the electron has returned to ground state
They have a set energy which corrosponds to a specific wavelength which produces a certain colour/em wave
What is in a fluorescent tube?
Mercury vapour
What is on the edge of the fluorescent tube?
A fluorescent coating which absorbs the photons and remittes them at a lower wavelength which means more can be seen and less are left as UV light
Why do we see missing colours in the light emitted from stars?
Because the gases in the stars atmosphere absorb certain wavelengths due to the excitation energy of that specific gas atom
How do we know light has a wave nature?
It can be diffracted, this can be shown by youngs double slit experiment
