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A level Physics - OCR A (New spec.) > Nuclear > Flashcards

Flashcards in Nuclear Deck (16)
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What three findings led to the standard model through Rutherford's experiment?

Most a particles travelled through gold foil with little deflection (EMPTY SPACE)

a particles deflected away from nucleus, repulsive force necessary (NUCLEUS CHARGED)


Why is radioactive decay described as a random and spontaneous event?

RANDOM: (1) Cannot predict when a particular nucleus will decay (2) Each nucleus within sample has the same chance of decay per unit time.

SPONTANEOUS: (1) Not affected by presence of other nuclei in the sample (2) External factors i.e. pressure


Fundamental Particle

No internal structure & cannot be split into smaller particles


Ionising Radiation

Radiation removes electrons from atom leaving it positively charged



Process by which unstable nuclei emit ionising radiation



Rate at which nuclei decay (Bequerels)



Process by which a particle and its antiparticle interact and their combined mass is converted to energy via E=MC^2


Binding Energy

Minimum energy required to completely separate a nucleus into its constituent protons and neutrons


Thermal Neutrons

Neutron in fission reactor wuth mean KE similar to the Thermal energy of particles in the reactor core - slow neutrons


Induced fission

Nuclear fission occurring when a nucleus becomes unstable on absorbing another particle (i.e. neutron)


Chain reaction

Reaction where neutrons from an earlier fission stage are responsible for further fission reactions leading to an exponential growth in the rate of reactions



Substance used to slow down the fast neutrons produced in fission reactions so they can propagate the fission reaction


With what forces do Quarks and Leptons intra-act?

Quarks = Strong Nuclear force

Lepton= Weak Nuclear Force


Why are gamma photons emitted?

When nucleus dropping to its ground state following the emission of an a or b particle.


Measuring intensity of gamma radiation from source with a count rate may not be reliable, why?

- Gamma rays emitted in all directions so the detector only records those emitted in one direction.
- The efficiency of the detector is not 100%, the detector only records a fraction of the gamma rays that pass through it.
- The body of the sample itself may absorb some of the gamma rays inside of it.


Describe what happens when a proton and antiproton meet, in terms if the photons (slow-moving)

Two Y-photons released with equal energy and travelling in opposite directions