Glossary

the A-Z of solar energy, units and prefixes

Definitions

biosphere - the regions on Earth and parts of the atmosphere that support or can support life

buoyancy - the upward force that a fluid (liquid or gas) exerts on an a substace less dense than itself when that substance is partially or completely surrounded by the fluid

diffusion - the scattering of incident light when it is refleced by an uneven surface; or, when light travels through a translucent material

dispersion - the process of separating a complex wave into its parts depending on a certain characteristic, like wavelength or frequency

electromagnetic radiation - combined electric and magnetic waves that are self-propagating and include radio waves, infra-red, visible light, ultra-violet light, X-rays and gamma rays

food chain - a progression of organisms in a biosphere that pass food energy from one to another as the organisms feed upon each other

frequency - the number of times per second that a process occurs or that a wave repeats itself

heat engine - a device that uses heat to do work

hydraulic - relating to the flow of a liquid

magnetic field - the field surrounding a permanent magnet or a charged particle that is moving; the Earth generates its own magnetic field

ozone layer - an area of the upper atmosphere, roughly 15 - 30km above the surface of the earth, that contains a high concentration of ozone molecules (O3); these molecules absorb ultraviolet radiation that are not affected by other parts of the atmosphere

relative humidity - a percentage which give the ratio of the quantity of water vapour in air, at a certain temperature, to the maximum quantity of water vapour that the air can hold at that temperature

thermonuclear reactions - at very high temperatures, the nucleii of atoms combine, or fuse; these reactions are the opposite of fission (breaking apart) reactions which happen in nuclear power plants

salinity - the conentration of salt in a solution

solar wind - a stream of charged particles moving at high speed radially away from the sun

wavelength - the distance (in metres, m) between consecutive peaks or consecutive troughs in a wave; for example, visible light has a range of wavelengths between 400 and 700nm (10-9m)

Units:

we use SI - Système International [d'Unités] - International System [of Units])

J - joule = a unit of energy; lifting an object of 1kg by approximately 10cm requires 1J of energy

W - watt = a unit of power; 1 joule per second;


W/m2 = watts per square metre; a unit of power per unit area

GJ = giga joule = 1,000,000,000 joules


Prefixes:

nano, n = 0.000000001; 10-9

micro, µ = 0.000001; 10-6

milli, m = 0.001; 10-3

centi, c = 0.01; 10-2

deci, d = 0.1; 10-1

deka, da = 10; 101

hecto, h = 100; 102

kilo, k = 1,000; 103

mega, M = 1,000,000; 106

giga, G = 1,000,000,000; 109