Flashcards
Particles and Radiation
Cards in this deck (20)
- 1What is Carbon DatingIt is a method used to find the age of organic material. It is done by finding the percentage of carbon-14 in the object and using the known starting value and its half-life to calculate an approximate age
- 2Strong Nuclear ForceIt keeps nuclei stable by counteracting electrostatic force of repulsion between protons in the nucleus. It only acts on nucleons and has a very short range being attractive up to 3fm and repulsive below 0.5fm
- 3Unstable NucleiHave either too many protons or neutrons causing SNF to not be enough to keep stable so these nuclei decay to become stable.
- 4Alpha DecayOccurs in large nuclei with too many protons and neutrons
- 5Beta-Minus decayOccurs in nuclei which are neutron rich
- 6AnnihilationParticle and anti-particle collide and their masses are converted into energy. This along with the kinetic energy of the two particles is released in the form of 2 photons in opposite directions to conserve momentum
- 7Pair ProductionPhoton is converted into equal amount of matter and anti-matter. This can only occur when photon has energy greater than the rest energy of the two particles.
- 8What are exchange particlesThey carry energy and momentum between particles experiencing force
- 9What are the exchange particles of each interactionSNF- Gluon
WNF- W boson
Electromagnetic- Virtual photon
Gravity- Gluon - 10What is the differentiating properties between hadrons and leptonsLeptons are fundamental particles and dont experience the SNF. Whereas hadrons experience the SNF and can be broke down further into quarks
- 11Conservation lawsIn particle interactions these must be conserved:
-Energy & Momentum
-Charge
-Baryon Number
-Lepton Number
-Strangeness (only in strong) - 12What is the photoelectric effectWhere photoelectrons are emitted from the surface of a material when light above the threshold frequency is incident upon it
- 13What is threshold frequencyThe minimum frequency required to liberate an electron
- 14Photon theory of lightThis suggests that EM waves travel in photons which have energy and frequency. Each electron can absorb a single photon, meaning an electron only emitted if frequency is greater than threshold frequency. If intensity increases and frequency above threshold, the rate of photoelectric emission increases
- 15Why can't wave theory explain photoelectric effectIt suggests that any frequency of light would cause emission as energy absorbed would gradually increase with each wave
- 16Energy LevelsElectrons in atoms can only exist in discrete energy levels. The electrons can gain energy from free electrons and move up an energy level, this is excitation. If they gain enough energy, they can be removed from the atom entirely. This is ionisation and it occurs if energy of free electron is greater than ionisation energy
- 17Fluorescent TubesThey are filled with mercury vaopur across which a high voltage is applied. This accelerates free electrons through the tube which collide with mercury atoms causing them to be ionised releasing more electrons which collide with more mercury atoms, causing them to excite. When they de-excite they release photons in UV range which excite atoms in the fluorescent coating which when they de-excite release photons in visual light range
- 18Line SpectrumLight from fluorescent tube shone through a diffraction grating or prism gives a line spectrum. Each line represents a different wavelength of light emitted by the source. The spectrum only contains discrete values of wavelength so energies emitted correspond to these. Therefore, providing evidence that electrons can only transition between discrete energy levels
- 19Line Absorption SpectrumIf you pass white light through a cooled gas you get this. It shows a continuous spectrum of all possible wavelengths with black lines at some which show possible differences in energy levels as atoms in gas can only absorb photons of energy equal to difference between energy levels
- 20Wave-Particle DualityIf light has particle properties, then particles should have wave like properties. Using the equation for De Broglie's wavelength you see that as momentum changes diffraction changes. If momentum increases, wavelength decreases and therefore diffraction decreases and interference pattern becomes closer
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- A level Physics Flashcards on Particles and Radiation, created by kian browne on 21/05/2024.
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- kian browne
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