particles Flashcards
ground state
the lowest energy state of an atom or other particle
Which wave are most stable
Whole numbers
De-exication
Elecrron isnt stable at higher energy levels, so it quickly returns to its lowest energy levels then a photon is emitted
Photoelectric effect
When a metal surface is illuminated with light, electrons can be emitted from the metal surface, provided the frequency of the light is above certain value
Where do the fastest electrons come from
Already at the surface
Photocell
Transfers light energy into electric energy
Produces a DC current
Larger area thr greater the power output
Advantage of photocell
No fuel needed
No power cables are needed
Long life
What is conserved?
Mass Baryon. Number Energy Charge Lepton number
What is line spectra
Line spectra consists of discrete lines, each typical of the element concerned
Absorption spectra
Spectrum observed is of a continuous coloured spectrum with dark lines in the position where the bright lines would have been in the emission spectrum.
The vapour absorbs specific frequencies from white light
Absorption spectra indicates what elements are present in stars
Red shift spectra suggests that galaxies are moving away from each other supporting the theory of the big bang
What does an emission spectra look like
A series of discrete bright lines against a black background
Explain how observation of absorption spectra helps to determine the element make up of a star
Aborsorption spectra are produced when white light passes through a cooler vapour. Dark lines appear where bright ones would have been in the emission spectrum for a particular element
Particles and antiparticles
Same mass
Opposite charge
Opposite spin
Opposite values of baryon number, lepton number and strangeness
Pair production
Particle and antiparticle can be produced by a high-energy photon
The photon must have enough energy to create the rest mass of the two particles
