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
Pair annihilation
Particle and antiparticle hit each other producing two photons
Lepton
Lightest group Acted on by the weak force Fundamental particle Electrons are stable (Neutrino)
Hadrons
Baryon and meason
Baryons
Heaviest
Made of quarks (3)
Only stable baryon is the proton
Mesons
Not fundamental
Quark and antiquark pair
Interactions with the strong force
Strangeness is conserved
Gravitation
Graviton
Between mass
Always attractive
Range is infinite
Electromagnetic
Photon
All charged bodies
Range is infinite
Weak nuclear force
W+, W-,Z0
Acts on all particles
Range of 10-17m
Responsible for b- decay
Strong nuclear force
Gluon
Acts on hadrons and mesons
Short range ( within the nucleus)
Bubble chamber
Contains liquid hydrogen
Ionises the hydrogen
Causing vaporisation and a trail of bubbles
Cloud chamber
Contains a pad soaked in a volatile liquid
As particles enter the chamber, the pressure is reduced so the liquid would condense onto the trail of ions
Alpha particles leave long straight paths
Range in air determined by initial kinetic energy
Spark chamber / drift chamber
Filled with gas at low temperature with thousands of parallel wires
A particle causes ionisation and electron drifts to the nearest wire. It then electronically time long long it takes the electron to reach the wire
