KEY TERMS Flashcards
Interference?
When two (or more) waves superpose/meet at a point - there is a change in overall displacement
Coherent?
Constant phase difference (between the waves)
Emission line spectra?
Where each element produces a unique emission line spectrum because of its unique set of energy levels
Continuous spectra?
All visible frequencies/wavelengths are present (e.g. of a lamp filament)
Absorption line spectra?
A series of dark spectral lines against the background of a continuous spectrum
Absolute scale of temp?
A scale for measuring temp based on absolute zero and the triple point of water (the difference between 1K-2K is the same as that of 1-2 degrees Celsius)
Absolute zero?
The lowest possible temperature - the temperature at which substances have minimum internal energy
Absorption/attenuation coefficient?
A measure of the absorption of X-ray photons by a substance (m^-1)
Acceleration?
The rate of change of velocity
Acceleration of free fall?
The rate of change of velocity of an object falling in a gravitational field (g)
Acoustic impedance?
The product of the density - of a substance - and the speed of ultra sound in that substance (Z, or Kgm^-2s^-2)
Acoustic/impedance matching?
The use of two substances with similar acoustic impedance to minimise reflection of ultrasound at the boundary between them
Activity?
The rate at which nuclei decay/disintergrate in a radioactive source - measured in becquerels/Bq or decays per second
Alpha radiation?
Ionising radiation consisting of particles made up two protons and two neutrons - a helium nucleus with Q=+2e
Amount of substance?
A measure of the amount of matter in moles
