IGCSE Physics Glossary (F-M)

focal length the distance between the optical centre of a lens and the principal focus
force a push or a pull
fossil fuel a fuel such as coal, oil or gas, formed over millions of years from the remains of living things
frequency the number of waves passing a point each second
friction the process that produces the force that opposes the movement of an object
fuse a device containing a wire that melts when an excessive current flows through it, thus breaking the circuit
gamma rays the part of the electromagnetic spectrum of waves that has the shortest wavelength and highest frequency
Geiger-Müller (GM) tube a device for measuring the radiation from a radioactive source
gravitational field strength the gravitational force acting on each kilogram of mass
gravity the process that produces the gravitational force between two objects
half-life the time taken for half the atoms in a sample of a radioactive isotope to decay
hertz (Hz) the unit of frequency = 1 cycle per second
incident ray the ray of light striking a mirror or an interface between two materials
infrared a type of electromagnetic radiation that has wavelengths just longer than visible light
insulator (electrical) a substance that is a poor conductor of electric current
insulator (thermal) a substance that is a poor conductor of internal energy
internal energy the energy a body has due to its temperature
ion an atom that has either gained or lost one or more electrons
ionisation the process of adding or removing an electron to or from an atom to form an ion
isotope nuclides that have the same number of protons, but different numbers of neutrons
joule (J) the unit of work and energy
kilogram (kg) the unit of mass
kinetic energy the energy that an object has due to its movement
latent heat of fusion the energy required to change solid to liquid with no change in temperature
latent heat of vaporisation the energy required to change liquid to vapour with no change in temperature
light dependent resistor (LDR) a device whose resistance changes when light shines on it
light emitting diode (LDR) a diode that gives out light when there is a current in it
linear (scale) a scale which goes up in equal steps for equal increases in the property being measured
logic gate an electronic processor that gives a digital output dependent on the states of its inputs
longitudinal (wave) a wave in which the particles vibrate parallel to the direction of travel of the wave
magnetic field the region in which a magnetic force acts
magnetic induction the process in which iron or steel becomes a temporary magnet when in a magnetic field
manometer a device used to measure the pressure of a fluid in relation to the atmospheric pressure
mass the amount of matter in a body
microwaves part of the electromagnetic spectrum that has waves of a wavelength between those of radio waves and infrared radiation
molecule a particle made up of two or more atoms
moment the turning effect of a force
motor effect the process in which a current carrying conductor in a magnetic field experiences a force
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