Chapter 26 - Nuclear Physics Flashcards
What are the two interpretations of the equation ΔE = Δmc²?
-Mass is a form of energy.
OR
-Energy has mass.
How is energy released/ absorbed in nuclear reactions?
Mass is converted to energy, or energy is converted to mass.
Describe annihilation.
Annihilation: an electron and positron annihilate each other, leaving two identical gamma photons travelling in opposite directions.
Describe pair production.
A single photon vanishes and its energy creates a particle and corresponding antiparticle.
Define mass defect.
The difference in mass between the nucleus and its separated nucleons.
Define binding energy.
The minimum energy required to separate a nucleus into its constituent nucleons.
What happens when total binding energy per nucleon is increased?
Energy is released.
Why does binding energy per nucleon start to decrease when elements get heavier than iron?
As nuclei get larger, the strong nuclear force holding nucleons together becomes weaker.
Define induced nuclear fission.
Nuclear fission that occurs when a nucleus becomes unstable from absorbing another particle.
What is meant when we describe fission as a chain reaction?
Neutrons that are released from one nucleus are absorbed by other nuclei, causing them to undergo fission.
Describe the basic structure of a fission reactor.
Fuel rods are spaced evenly in the reactor core, surrounded by a moderator (usually water (this also acts as a coolant)). Control rods can be moved in & out of the core.
What is the purpose of the moderator?
To slow down the fast neutrons produced in fission reactions, so they don’t bounce off fuel nuclei.
What is the purpose of the control rods?
To absorb neutrons and slow down/stop the fission reaction.
What are the main issues of nuclear waste?
It is extremely toxic and radioactive, with a very long half life. It must be buried deep underground so it does not enter food/water supplies.
Define nuclear fusion.
The process by which light nuclei are joined to produce heavier nuclei.
Why is a high temperature required for fusion reactions?
Nuclei move fast enough to overcome the strong nuclear force repelling them.
