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16 Cards in this Set
- Front
- Back
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Absolute thermodynamic scale of temperature |
A temperature scale which is independent of any specific substance. Measured in kelvin. |
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Absolute zero |
The temperature at which a substance has minimum internal energy; this is the lowest limit for temperature. |
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Absorption line spectrum |
The pattern of dark lines in a continuous spectrum from a light source caused by light passing through an absorbing medium such as a gas. The dark lines represent the wavelengths that are absorbed. |
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Acoustic impendance |
Defined by the equation Z=pc where p is the density of the material and c is the speed of sound in the material. The unirs are kgm^-2 s^-1. |
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Activity |
The number of nuclear decays (the number of gamma rays emitted) per unit time. An activity of one decay per second is called one becquerel (Bq). |
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Alpha-particle |
A particle comprising two protons and two neutrons ejected from the nucleus during radioactive decay. It is identical to a helium nucleus and is emitted due to its unusually high stability as a particle. |
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Alternating current |
Electrical current that reverses its direction with a constant frequency. For example, the UK mains electricity supply is a.c. with a frequency of 50 Hz. |
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Amplitude |
The maximum displacement, measured in meters. Will always be positive. |
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Angular frequency |
The product 2πf or 2π/T and has the units radians per second, rads^-1. |
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Angular velocity |
The rate of angular rotation, measured in radians per second, rads^-1. |
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Annihilation |
The process by which a particle and an antiparticle interact and their combined mass is converted to energy. The energy released is given by E=mc^2. |
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Antiparticle |
A particle of antimatter that has the same rest mass but, if charged, an equal and opposite charge to its corresponding particle. For an example the positron (e+) and the antiparticle the electron (e-). |
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Astronomical Unit (AU) |
The mean distance from the centre of the Earth to the centre of the Sun. |
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Attenuation and attenuation coefficient |
A gradual decrease in intensity. A constant is used to calculate how the intensity of X-rays decrease as they pass through a material. The unit is m^-1. |
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Avogadro constant |
The number of particles in one mole of a substance. This constant has the symbol NA = 6.02 x 10^23 mol^-1. |
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Beta-minus decay |
Decay in which a neutron in the nucleus breaks down into a proton under the influence of the weak nuclear force, and a beta-minus particle and an electron antineutrino are emitted. A beta-minus particle is an electron. |
