Radiation Flashcards
What is the photoelectric effect
Electrons on metal surface absorb energy from light and electrons are released as photoelectrons.
What are the 3 theories of the photoelectric effect
No photoelectrons are emitted is has frequency under threshhold frequency.
PE emitted with variety of kinetic energies . Value increases as frequency inc. Unaffected by the intensity radiation.
Number og photoelectrons emmitted per second is proportional to the intensity of radiation
Why couldn’t the photoelectric effect be explained by wave theory
Higher intensity , the more energy should transfer to each electron ; the kinetic energy should increase the intensity.
NO explanation for kinetic energy depending on frequency. No explanation for threshold frequency.So electrons should be emitted eventually no matter frequency.
WHat is the threshold frequency
f = Work function / h
Describe the distribution of kinetic energy to lost electrons
Electrons depper down electrons , lose more energy
Kinetic energy is independent of the intensity , as only absorb one photon at a time.
WHat is stopping potential
The p.d needed to stop the fastest moving electron.
Explain hoe fluorescent tubes uses excited electrons
COntain mercury vapour.
Fast moving electrons collide with mercury atoms
Mercury electrons become excited to a higher energy level.
WHen they de-excite , the emit a photon.
Phosphor white coating absorb these photons ,exciting its electrons.
When it de-excites , it emits visible photons in the form of visible light
What are line emission spectra
With prism or diffraction grating.
Series of bright lines against a black background.
Show particular wavelength of light emmitted corresponding to emitted photon energies of different wavelength
What are absorption spectrums
Wavelengths of emitted photons are missing from a continuous spectrum.
Black lines represents the absorbed wavelengths against a coulur spectrum
What shows light behaving as a particle
Photoelectric effect,
Photons , bundles of energy interact with electrons one-to-one.
Photon is given to one electron
What shoes light behaving as a wave
Interference and diffraction paterns.
Explained by waves interfering constructively or destructively
Describe what shoes the wave nature of electrons
Diffraction patterns when electrons interact.
Small acc voltage , slows electrons , wide spaced rings.
Inc electron speed and the diffraction patten squashes together.
