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Glossary
A
Atom - The most basic form of an element that can exist. Atoms are made up
of a positively "CHARGED" nucleus surrounded by very small and light
negative electrons. The nucleus itself is made up of positive protons and
neutral (uncharged) neutrons.
B
Beta Particle - A form of nuclear ionising radiation. It is produced when a
neutron in an unstable nucleus is transformed into a proton, and emits an
electron. The electron is the beta particle. They travel at around 90% of the
speed of light and are stopped by a few mm of aluminium.
Black Hole - A region of space that has gravity so strong that not even light
can escape from it. Anything entering a black hole is lost forever. The edge of
a black hole is called the "event horizon", and this is the part you mustn't
cross. Although black holes are strictly speaking still a theory, there is strong
evidence to support their existence. It is thought that black holes exist at the
centre of some galaxies, and inside "QUASARS"
Blue-shift - When an object is moving towards us very quickly, the light
waves coming from it become compressed, so that when they reach us they
are of shorter wavelength (and higher frequency) than when first emitted.
Catalyst - A chemical substance that helps to speed up a chemical reaction
Charge - Charge is a property of an electron (-), a proton (+) and many other
"SUBATOMIC PARTICLES". The unit of charge is the COULOMB (C). The
charge on one electron is VERY small; -1.6 E-19 C
(0.00000000000000000016C). Moving charge results in an electric
"CURRENT".
D
Diffusion - Movement of molecules from a place of high concentration to a
place of low concentration.
Dielectric - The non conducting layer separating two plates in a capacitor.
The properties of the dielectric govern the maximum working voltage of the
capacitor and the capacitance of the capacitor.
E
Electron - "FUNDAMENTAL PARTICLE" with negative charge. One of a
group of particles called "LEPTONS", it has a charge of -1.6 E-19 C
(0.00000000000000000016 C) and a mass of 1/1860 u.
Energy - this is the capacity for doing work. Whenever anything is done,
energy is involved, being converted from one form to another. There are many
types of energy, such as Gravitational potential, Elastic potential, Electrical
potential, Heat, Light, Kinetic (movement), Nuclear, Chemical potential. In
any energy conversion, the TOTAL energy is always conserved. Energy
cannot be created or destroyed, but is converted from one form to another
- the Principle of Conservation of Energy.
Equilibrium - There are different types of equilibrium (eqm), such as chemical
eqm. In physics we normally work with mechanical eqm. A system is in
equilibrium if
i) the total "FORCE" acting in any direction is zero, and
ii) the total "MOMENT" about any point is zero.
F
Force - An entity which may cause acceleration, deformation, rotation,
sheering etc. A force is a push or a pull. The unit of force is the newton (N).
Examples of forces are weight (caused by gravity), friction and tension.
Fundamental Particle - One of the most basic building blocks of matter.
These particles cannot be broken down any further (as far as we know!).
Electrons and Quarks (Which make up protons and neutrons) are examples of
fundamental particles
G
Gamma Radiation - A high energy form of electromagnetic radiation. It is
emitted from a nucleus, usually after the nucleus has undergone an alpha or
beta decay. It is weakly ionising, it has no charge and it has no mass.
Gamma rays are reduced by thick lead, steel and concrete.
Galaxy - A huge collection of around 100 000 000 000 "STARS" (One
hundred thousand million, or one hundred billion). A galaxy may be spiral,
elliptical or irregular. We inhabit a spiral galaxy called the "milky way".
H
Haemoglobin Iron - containing pigment that carries oxygen in the blood.
Hormone - A protein molecule that is secreted from a gland into the blood.
It changes the function of other cells around the body.
Hydrotropism - Growth of a plant in response to the presence of water.
I
Isotope - Isotopes of the same element have the same number of "PROTONS"
but different numbers of "NEUTRONS". If two atoms have different numbers of
protons then they must also have different numbers of electrons in order to be
electrically neutral. They therefore have different chemical properties and are
atoms of different elements altogether.
J
Joule (J) - The unit of energy. 1 joule is the kinetic energy of a mass of 1kg
moving at 1m/s. 4200J of heat energy is required to raise the temperature
of 1kg of water by 1 deg. Celcius.
K
Kelvin - Named after Lord Kelvin, this is also called the absolute temperature
scale. The interval of 1 Kelvin (1K) is equal to 1 degree Celcius. Absolute
zero (0K) is -273.15 deg. Celcius. To convert a temperature in deg. Celcius
into Kelvin, add 273.15.
L
Light - Pure electromagnetic energy. It may or may not be visible. See
"ELECTROMAGNETIC SPECTRUM"
M
Mass - The amount of matter an object contains. The unit of mass is the
Kilogram. Note that mass is not the same as "WEIGHT". Weight is a force, and
so has the units "newton".
Momentum - NOT TO BE CONFUSED WITH MOMENT, this is a quantity which
something has because of its motion. MOMENTUM (kgm/s)= MASS(kg) x
VELOCITY(m/s).
N
Nucleus - The control centre of plant and animal cells which contains the
genetic information.
Nucleus - The tiny central part of an atom, occupying little space but
carrying almost all of the mass of the atom. Made up of protons and
neutrons
Neutral - Without electric charge
Neutron - A neutral particle in the nucleus of an atom. It is made up of three
quarks (dud). During a beta decay, the neutron is converted to a proton and
an electron is emitted. The electron is the beta particle
O
Optimum - The conditions (temperature, pH, etc.) at which the enzyme works
best
P
pH - A scale from 1 (acid) to 14 (alkaline) that measures acidity and
alkalinity
Product - The chemical molecules left at the end of a reaction
Q
Quark - A fundamental particle. There are 6 known types of quark (UP,
DOWN, STRANGE, CHARM, TOP, BOTTOM) although all the nuclear matter in
the known universe is made up of UP and DOWN. Quarks exist in triplets (a
proton is made up of UP, UP, DOWN) or Quark-Antiquark pairs (see
"ANTIMATTER").
R
Radiation- Radiation is a form of energy that emitted from some chemical
process. It contains of wavelength, frequency.
S
Scalar - Scalar quantities only have size (also called magnitude). They do not
need to have a specified direction. Examples of scalars are "SPEED",
"MASS", "ENERGY", "TEMPERATURE".
T
Temperature - How hot something is, measured in degrees Celcius or
Kelvin. It is NOT the same as heat, which is a form of energy, measured in
joule. To illustrate this, consider a spark and a kettle of boiling water. The spark
may be at several hundred degrees celcius, but will harm you less than a kettle
full of water at only 100 deg. celcius. This is because the water contains more
heat energy in total.
U
Ultrasound - Sound which is at a "FREQUENCY" higher than can be heard
by the human ear is called ultrasound. It displays all the usual wave
properties, such as reflection, refraction and diffraction, and has many uses.
Typical examples are monitoring unborn children, monitoring blood flow
and echo-sounding. In echo-sounding, pulses of ultrasound are reflected off the
seabed or off shoals of fish and the time taken to receive the reflection is used to
calculate depth.
V
Vector - A quantity which has size (also called magnitude) and direction. (As
opposed to a "SCALAR" which only has size). Examples of vectors are
"FORCE", "VELOCITY", "ACCELERATION", "WEIGHT", "DISPLACEMENT
W
Wavelength - The distance between two troughs or two peaks on a wave.
Weight - This is the "FORCE" with which something is attracted to the Earth.
Weight (N)= mass(kg) x gravitational field strength(N/kg).
X
X-ray - Part of the electromagnetic spectrum. X-rays travel through some
materials but not others, and they show up on photographic film. These
properties make them ideal for medical uses, such as scanning for broken
bones. Over exposure to X-rays can be dangerous, and so people who work
with them all the time use screens to shield them from the rays.