L

lag - relative phase of a current or voltage in an a.c circuit
lamina - flat object like piece of card
laminations - thin, flat plates as in a laminated core in a transformer
laser - 'light' source giving a fine intense beam of monochromatic coherent radiation
latent - hidden or stored, as in latent heat
latent heat - energy required to change the state of a sample, either fusion or vaporisation
lateral - side to side as in 'lateral inversion' in a plane mirror
lath - thin, flat strip of wood used in air pressure experiments
law - a statement, usually mathematical, that describes a physical phenomenon
LC - circuit, one containing an inductor and a capacitor
LCD - liquid crystal display
LDR - light dependent resistor
LED - light emitting diode. A diode that gives out light.
lee's disc - apparatus for measuring the conductivity of a poor conductor
left hand rule - a way of finding the direction of a magnetic field using your left hand
lens - a device for focussing or spreading out a light beam (note spelling with no e!)
lenses - plural of lens - note spelling with an e!
lenz's law - the direction of the induced current opposes the change producing it
Leonids - meteor shower peaking on 17^th November
lepton - particle that interacts with others by gravitational and electro weak forces alone
Leslies cube - apparatus use to study the emission of radiant heat energy from different surfaces
libration - apparent rocking motion of the Moon's axis due to its elliptical orbit (see > 50%)
lift pump - pump that works using atmospheric pressure only
light - visible electromagnetic radiation with wavelengths between 400 nm and 700 nm
light gate - timing device based on the principle of interrupting a light beam
light gathering power - the ability of a telescope to collect light
lightning - large electric spark in the sky, between clouds or between a cloud and the ground
light pollution - scattering of light from man made sources across the night sky. A serious problem
light year - distance light travels in a year (about 9440 000 000 000 km)
linear - in a straight line, as in linear motion (sometimes rectilinear)
linear air track - apparatus for investigating motion - straight track with air holes
linear accelerator - apparatus for accelerating charged particles in a straight line
liquid - state of mater with a fixed volume but a shape that depends on the container
liquid crystal - long molecules retaining some liquid properties, many materials optically active
litre - unit of volume (1000 litres = 1 cubic metre, 1000 cm³ = 1 litre)
lodestone - naturally occurring magnetic ore
logic gate - electronic component that can perform simple decisions, AND, OR, NOT etc.
longitudinal - vibration along the direction of motion, as in a longitudinal wave
loudspeaker - device that converts electrical energy into motion and then sound energy
lower fixed point - temperature at which pure water freezes under normal atmospheric pressure
lumen - unit of luminous flux
luminescence - emission of light from an object by a process that does not involve heat energy
luminous - something that gives out light e.g. the Sun, a star, a flame
luminous flux - the flow of light energy from a source
lunar - referring to the Moon
lunar eclipse - the Earth moves between the Sun and the Moon; Sun's light to the Moon is cut off
Lunik - a series of Soviet Moon probes
lux - unit of illumination. 1 lumen per square metre
Lyman series - series of lines in the hydrogen spectrum all with wavelengths in the ultra violet
Lyrids - meteor shower in the constellation Lyra peaking around 22^nd April