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
Ampere?
Base unit of electric current - the current flowing in two parallel wires in a vacuum 1m apart, so that there is an attractive force of 2.0 x 10^-7 N per metre length of wire
Amplitude?
The maximum displacement from the equilibrium position (pos or neg)
Angle of incidence?
The angle between the direction of travel of an incident wave and the normal at a boundary between two media
Angle of reflection?
The angle between the direction of travel, of a reflected wave, and the normal at a boundary between two media
Angular frequency?
A quantity used in oscillating motion - it equals the product of 2 x pie x frequency
Angular velocity?
The rate of change of an angle for an object moving in a circular path
Anion?
A negatively charged ion - attracted to the anode
