Definitions unit 5 Flashcards
Internal energy
Some of kinetic energy and potential energy of particles/molecules in a substance
Ideal gas
Obeys Boyles Law at all temperatures It behaves in a particular way has negligible size elastic collisions identical molecules and number of particles is sufficient
Absolute zero
0K temperature at which particles have no kinetic energy and therefore no vibrations
Background radiation
Constant level of radiation both past and present for example radon gas, cosmic rays, isotopes, food and drink, rocks and soil
Alpha
Helium nucleus highly ionising charge of +2 emitted to make nuclei more stable
Beta
Fast-moving electrons or positron emitted by an atomic nucleus undergoing radioactive decay
created when a neutron becomes a proton
Gamma
High-energy electromagnetic wave
Spontaneous decay
Cannot be influenced by external forces
Random nature of decay
Cannot predict when it will decay
Stable
Sufficient amount of energy unlikely to decay
Half life
Time taken for number of nuclei to decrease to half the original number
Activity
Number of decays per second
Binding energy
Energy required to separate nucleus into constituent parts
Mass deficit
Difference between mass of nucleus and the sum of its constituent nucleons
Fission
Not having nucleus splits into two more stable nuclei with the emission of neutrons
Fusion
Joining of two smaller nuclei into one more stable nucleus with the release of energy
Flux
Power per-unit area
Luminosity
Rate of energy transfer
Inverse square law
For example a is proportional to 1/b^2
Standard candle
Astronomical object of known luminosity
Exponential
Fractional change in y is same as each incremental change in x
Power law
y=ax^n
log(y)=log(a)+nlog(x)
Black body radiator
A black body is one absorbs all wavelengths of radiation falling on it at all temperatures, this means that the energy flex omitted depends only on the bodies temperature and not its composition
The Doppler effect
An change in the frequency relative to the movement of the source from the observer
