Definitions Flashcards
OCR A-level physics definitions on everything
absolute scale of temperature
a scale for measuring temperature based on absolute zero and the triple point of pure water, with gradations equal in size to those of the Celsius scale
unit: kelvin (K)
absolute zero
the lowest possible temperature, the temperature at which substances have minimum internal energy
absorption coefficient (attenuation coefficient)
a measure of the absorption of X-ray photons by a substance.
unit: m-1
absorption line spectrum
a set of specific frequencies of EM radiation, visible as dark lines in an otherwise continuous spectrum on spectroscopy.
they are absorbed by atoms as their electrons are excited between energy states by absorbing the corresponding amount of energy in the form of photons- every element has a characteristic line spectrum.
acceleration
the rate of change of velocity,
a vector quantity
acceleration of free fall
the rate of change of velocity of an object falling in a gravitational field
symbol g 9.81ms-2
acoustic impedance
the product of the density (p-row) of a substance and the speed (c-speed of light) of ultrasound in that substance -
symbol Z
unit kg m^-2 s^-1
acoustic matching (or impedance matching)
the idea of two substances with similar acoustic impedance to minimise reflection of ultrasound at the boundary between them
activity
the rate at which nuclei decay or disintegrate in a radioactive source, measured in bequerels (Bq) or decays per second
alpha radiation
ionising radiation consisting of particles compromising two protons and two neutrons (a helium nucleus)
charge: +2e
air resistance
the drag or resistive force experienced by objects moving through air
ammeter
a device used ri measure electric current - it must ensure placed in series and ideally have zero resistance
amount of substance
a measure of the amount is matte in moles
ampere
the Base SI unit is electrical current, symbol A, defined as the current flowing in two parallel wires in a vacuum 1 my apartment such that there is an attractive force of 2.0 × 10^-7 per metre length of wore between them.
amplitude (waves)
the maximum displacement from the equilibrium position (can be positive or negative )
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 oscillatory motion - equal to the product of frequency (f) and 2 (pie)
angular velocity
the rate kf cha very of an angle for am object moving circular path - symbol (w)
anion
a negatively charged ion, one which is attracted to am anode
annihilation
the complete destruction of a particle and it’s antiparticle in an interaction that releases energy in the form of an identical photons
anode
a positively charged electrode