Paper 1- Quantum phenomena Flashcards
What does the photoelectric effect suggest?
The particle nature of light
Using the particle theory of light, what effect does increasing the intensity have on the photelectric effect?
More electrons liberated
Why does a particle model of light support the photoelectric effect?
Electrons will be liberated by a low intensity light of the right frequency.
1:1 interaction of photons and electrons
Does a wave theory of light support the photoelectric effect?
No
Work function definition
The energy needed to remove an electron from the surface of a metal
What are the 3 laws of photoelectric emission?
1) when incident light is monochromatic, no of e- per sec is proportional to intensity
2) Ek varies from 0 to a definite max and is only dependent on frequency
3)No e- emitted when frequency lower than threshold frequency
Why are electrons emitted with a range of energies when the source is monochromatic?
Electrons emitted from different layers in metal and lose energy moving up to surface
Using the particle theory, what effect does increasing the frequency have on the photoelectric effect?
Higher Ek (max)
How to calculate frequency of a wave
Speed of light/ wavelength
If wave theory was correct, what effect would increasing the intensity have on the photoelectric effect?
Higher Ek(max)
If wave theory was correct, what effect would increasing the frequency have on the photoelectric effect?
No effect
Why does a wave theory of light not support the photoelectric effect?
No electrons emitted if a very bright low frequency light is used
How does the fluorescent tube work?
Electrons collide with atoms of mercury vapour and excite them
Electron returns to ground state emitting a UV photon
Phosphor absorbs UV photon and gets excited
As electron returns to ground state it emits 3 visible light photns
What do the gaps in line spectra of hydrogen show?
The frequencies of light that are absorbed by the hydrogen atom and therefore the energy levels of hydrogen
What does electron diffraction suggest?
The wave nature of particles
What explains the particle nature of electrons?
They can be deflected by electric and magnetic fields
What is the deBroglie wavelngth?
The wavelength of a particle
