Electrostatic	Branch of electromagnetic theory dealing with electric charges at rest.
Element	One of the fundamental chemical substances that cannot be divided into simpler substances by chemical means. Atoms with the same atomic number (number of protons) are the same element.
Emission spectra	Light which is emitted by atoms and which is broken into its component colors. The emission specturm of each elelment is unique to that elelment.
Energy	The ability of one system to do work on another system. It is measured in Joules.
Energy band	A group of closely spaced allowed energy levels for a group of closely spaced atoms.
Energy band creator	A computer program that allows the user to learn about the potential energy diagrams for single atoms, multiple atoms and a solid with impurities. The program allows the user to determine what the energy levels that an electron bound to an atom can possess. Also the program allows the user to determine the energy levels and energy bands for multiple atoms and solids with impurities.
Energy band diagram	The graphic representation of energy bands.
Energy diagram	The graphic representation of energy levels.
Energy gap	The difference in energies between the Conduction Band Edge (Ec) and the Valence Band Edge (Ev).
Energy level	The sum of the kinetic and potential energy possessed by a particle and described by the wave packet. According to quantum mechanics, in some cases a particle cannot have any arbitrary value of total energy, but rather can exist only in certain states with certain specific values of total energy. These states are called energy levels.
Energy, allowed	Sets of available energies for a particle.
Energy, electrical	The transfer of work, by an electrical field, on a charge to create a current within a circuit.
Energy, total	The sum of all forms of energy possessed by an object.
Equilibrium	A state where the critical parameters of a system do not significantly change. When the time frame is infinite, it is called a Thermodynamic Equilibrium. A small change in a critical parameter leads to an unstable equilibrium state. An equilibrium is stable when a small change in a critical parameter leads to a "restoring force" which tends to return the system to equilibrium.
eV (electron-volt)	A unit of energy equal to the change in energy for an electron moving between 2 points in an electric field with a potential difference of 1 volt. 1 eV = 1.60 x 10-19 J.
Excited state	An energy level which has a higher energy than the ground state of an atom or nucleus.
Excited state band (conduction band)	An energy band where electrons have sufficient energy to break free from their respective atoms and conduct electricity.
Exponentially	Describes an increase or decrease in a variable which can be expressed as ex, where e is a fixed constant.
Fermi energy	The energy at which the probability of finding an electron of lesser energy than it is one-half (and hence the probability of finding an electron of greater energy than it is also one-half). The fermi energy of an intrinsic semiconductor is exactly midway between the conduction band edge (Ec) and the valence band edge (Ev) in the energy gap at absolute zero. If the semiconductor is heated, the fermi energy increases. The fermi energy of an N-type semiconductor is closer to the conduction band edge while that of a P-type semiconductor is closer to the valence band edge. If the number of dopant atoms (either donors or acceptors) is very large, the fermi energy might shift into the conduction band or the valence band. Such a semiconductor is called a degenerate semiconductor and can function as a tunnel diode.
Filament	The fine metal wire in a light bulb that becomes incandescent when heated by an electric current. Also, The cathode of a thermionic tube, usually in the form of wire, that may be electrically heated.
Fireflies	Member of the beetle family (Lampyridae). Males are winged. Females are wingless and are often called "glow worms." Both males and females produce intermittent bioluminescent light emission for attracting mates.
Fluorescence	The phenomenon exhibited by certain materials that can absorb radiation and convert it into light.
Fluorescent dye	A chemical substance that changes color in fluorescent light.
Fluorescent lamp	The process of light emission that involves the absorption of high energy ultraviolet (uv) light by the phosphor coating and the subsequent emission of visible light.
Foil	A very thin sheet or leaf of metal.
Force field	The strength of the repulsive force experienced when an electron is incident upon a potential barrier. It depends upon the gradient, or slope, of the potential barrier.
Function	An association between two sets in which an element of one set has one assigned element in the other set. Any selected element becomes the independent variable and its associated element is the dependent variable.
Gas discharge tube	A device in which a gas or metal vapor conducting an electric discharge is the source of light.
Gas lamp	A device in which a gas or metal vapor conducting an electric discharge is the source of light.
Gaussian	Describes the bell-shaped graphical curve that represents the probability of finding an object at a specific point. It indicates that the probability is maximum at a certain point and then falls off very rapidly as the curve moves horizontally in either direction away from that point. A wave packet describing such a probability is called a Gaussian wave packet.
Glow -in-the dark	A common term for a phosphorescent object.
Graphite	A soft, black, lustrous form of carbon found in nature and used for lead in pencils, lubricants, and electrodes.
Ground state valence band (ground state band)	The electron state with the lowest possible energy for that atom. An energy band in which electrons do not have sufficient energy to break free from their respective atoms and hence do not conduct electricity. These electrons are tied to their respective atoms.
Heat	A measure of the amount of energy transferred from one body to another because of the temperature difference between those bodies.
Heisenberg’s Uncertainty principle	Pairs of measurable quantities that have a product of energy×time dimensions, called conjugate quantities in quantum mechanics. They have a special relation to each other, expressed in Heisenberg’s uncertainty principle. The principle states that the product of the uncertainties of the two quantities is no smaller than h/2(pi). Thus if the measurement precision of one quantity is improved the precision of the other gets worse.
Helium	(He) The second most common and second lightest element in the universe.
Hydrogen	(H) The most common and lightest element in the universe.
Impurities	(dopants) Trace amounts of a substance added to a pure semiconducting material. The added impurities make a semiconductor an electron acceptor or donor, enabling current to be produced.
Impurity state band	Describes impurity atoms that are added to the solid, resulting in a formation energy bands found inside the band gap of the material. The placement of this band of energies depends on nuclear charge of the impurity atoms found in the solid.
Incandescence	Describes light generation created by high temperatures.
Incandescent lamp	A lamp with a filament which is contained in a partial vacuum and heated to incandescence by an electric current.
Incident	An adjective used to describe one object striking another object.
Infrared	Describes the light portion of the EM (electromagnetic) spectrum with long wavelengths that are undetectable to the human eye (3.0 x 10-3m to 3.0 x 10-6m).
Intensity	The amount of energy per unit time per unit area.
Intensity spectrum	A graph of the intensity of light versus color (or wavelength or energy).
Interaction	A process in which a particle decays or responds to a force caused by the presence of another particle (as in a collision). Also used to mean the underlying property of the theory that causes such effects.
Interference	Describes two waves that propagate through the same region of space. Neither wave is altered, but the amplitudes of the waves add (or cancel, if they are not in phase) to give the total effect to the medium at that point.
Inversely proportional	The relation between two quantities where as one increases the other decreases, and vice versa.
Jelly fish	Marine creature (phylum Cnidaria) characterized by lack of body cavity and brain. Jellyfish have a soft, jelly-like, bell-shaped body and tentacles with toxins. Some deep-sea varieties exhibit bioluminescence.
Joule	A Joule (J) is the SI unit of work and energy. [1J]=[1Newton].[1meter].
Kinetic energy	Energy associated with the motion of a particle. The kinetic energy of a particle is proportional to the square of the speed of the particle.
Lamp, tanning	A light source used to tan human skin.
Lantern fish	Small, deep-sea, bony fish (family Myctophidae) that demonstrate bioluminescence though glands on the body.
Laser	Light Amplification by Stimulated Emission of Radiation. A device that utilizes the natural oscillations of atoms for amplifying or generating electromagnetic waves.
Laser diode	A semiconductor diode that emits light when conducting current. The emission of light occurs when electrons cross the P-N junction and is of a much higher intensity than an LED.
Lattice	A systematic three-dimensional arrangement of objects -- real or imaginary -- as in crystal molecules.
LED	see Light Emitting Diode
Light Emitting Diode (LED)	A semiconductor diode that emits light when conducting current. The emission of light occurs when electrons cross the P-N junction.
Light stick	A cylindrical plastic tube that when twisted or broken combines chemicals that produce light.
Light, cool	Light given off without thermal radiation -- that is, without heat.(See also Luminescence)
Light, hot	White, glowing, or luminous light with intense heat. (See also incandescence)
Light, visible	The part of the electromagnetic spectrum to which the human eye is sensitive. It extends from a wavelength of about 380 nanometers for violet to about 760 nanometers for red light.
Line spectrum	Discrete, not continuous, spectrum in which a series of lines of different colors appears.
Linearly proportional	Two quantities in which as one quantity increases, the other increases. Also if one quantity decreases, the other decreases. In both increase and decrease the relation between the two quantities can be graphed as a straight line.
Localized	Confined to a specific location or small region of space.
Logic elements	Are electronic components that perform logic operations like the "and," "or," "and," and "nor."
Luciferase	An enzyme that catalyzes the oxidation of luciferin.
Luciferin	A pigment found in luminescent organisms (as fireflies) that furnishes practically heatless light.
Luminescence	Emission of light created by a chemical reaction at relatively low temperatures.
Magnetic field	The area surrounding a moving electrical charge. The vector field that influences charges within it.
Magnetic probe	An instrument that is used to penetrate, poke, or prod in an exploratory way.
Magnitude	Size. A number assigned to a quantity so that it may be compared with other quantities in the same class.
Mass	A quantity of matter cohering together to make one body. Mass is the property that causes a body to have weight in a gravitational field.
Matter	The substance that composes a physical object.
Mechanoluminescence	The emission of light as a response to a mechanical stimulus.
Mercury	(Hg) A transition metal that is liquid at room temperature; also called "quicksilver."
Metastable state	A state of instability. Specifically, an atom that cannot emit radiation without an additional supply of energy.
Microelectronic	Very small scale electronics, where the size of the components is microscopic.
Molecular	Relating to, connected with, produced by, or consisting of molecules.
Momentum	Mass multiplied by velocity.
Motion detector	A device that senses the movement of objects.
Multi-color LED	An LED that can emit light of different colors depending upon which pair of leads is connected to the battery.
Nanomachines	Extremely small machines (a few nanometers in dimension) that can be used to manipulate atoms and other objects of similar dimensions.
Nanometer (nm)	A unit that equals one billionth (10-9) of a meter.
Nanoscale	A term referring to phenomena or objects that are observable within distances of a few nanometers.
Nanostructures	Objects that have a size of a few nanometers.
Nanotechnology	The process of building and using for practical purposes objects which have sizes of a few nanometers or less.
Negative energy	Energy of an electron in a bound state in an atom,with the reference chosen as the energy outside the atom, very far away from the nucleus.
Neutron	An uncharged elementary particle in which the mass nearly equals the mass of a proton and no electrical charge.
N-side	(See N-type semiconductor)
N-type semiconductors	A semiconductor that contains fewer acceptors than donors and hence has a net abundance of electrons.
Nucleus	The positively charged central portion of an atom that comprises nearly all of the atomic mass and that consists of protons and neutrons (except in hydrogen in which it consists of one proton only).
Ohm’s law	The relation among electrical current, voltage and resistance. It is normally written as Voltage = Current x Resistance or V = IR.
Ohms (W )	A unit of electrical resistance.
Open circuit voltage	Voltage generated when two terminals are connected through a voltmeter that has infinite resistance. The current is therefore not complete.
Oscillation	Describes material that swings or moves back and forth from point to point -- like a pendulum.
Phase	An angle that describes the relative angle between two oscilating objects or between two waves.
Phenyl oxalate ester	A chemical used in light sticks.
Phosphorescence	Light emission that is perceptible with characteristic rate of decay after the exciting cause ceases to act on the object.
Phosphorescent	Exhibiting or characterized by photosphorescence.
Photoluminescence	Light emission caused by exitation producted by visible or invisible light
Photoluminescent	(see photoluminescence)
Photon	A massless elementary particle that is the carrier of radiant energy. A photon is a bundle of energy.
Photosynthesis	The formation of carbohydrates from carbon dioxide and a source hydrogen (as water) in chlorophyll-containing cells (as of green plants).
Pions	PI-MESON, one of the elementary particles in nature.
Pistons	A piston is a sliding piece moved by or moving against fluid pressure.It usually consists of a short internal cylinder that moves back and forth within a cylindrical vessel.
Planck’s constant	Multiplied by frequency of a photon to calculate the energy of the photon.It was proposed by Planck in the context of the quantization of energy. (6.626 x 10-36J/s)
Plankton	Very tiny plant and animal organisms that are found in large numbers in fresh or salt water. Some groups show visible bioluminescence.
P-N Junction	A junction of two pieces of semiconductor material, one P-type and the other N-type.
P-N Junction area	The cross sectional area of the P-N junction over which the P-side and N-side are in contact with one another.
Polymer	A material made of many, large molecules connected together in long chains.
Position	The location of an object at a particular point in space.
Potential barrier	An abrupt increase in the potential energy of a particle. It is analogous to a wall that obstructs the motion of a ball thrown toward it.
Potential energy	The energy of a particle due to its position, for example, the energy of a ball that is held above the surface of the earth.
Potential energy diagram	A graph of the potential energy versus distance.
Potential well	A decrease in potential energy in a small region of space. It is the opposite of a potential barrier.
Potentiometer	An electronic device (also called a variable resistor) in which electrical resistance can be varied.
Power supply	A voltage source that provides electrical energy (for example, a battery).
Probability	The chance or likelihood of a particular event occurring, expressed as a number from 0 (no chance) to one (100% certainty).
Probability density	The square of the wave function representing a particle. The value of the probability distribution function at any point in space physically represents the probability of finding the particle at that point in space.
Probe tip	A fine metal tip that is used by the scanning tunneling microscope to generate an image of an extremely small object.
Proton	A positively, electrically charged elementary particle found in the nucleus. It has a mass almost 2000 times that of an electron.
P-side	One of the types of semiconductors that makes up a solid-state device (for example, an LED) in which impurity atoms have been added that have a deficiency of electrons. These impurity atoms are called acceptors.
P-type semiconductor	A semiconductor that contains more acceptors than donors and hence has a net deficiency of electrons.
Quantized	Describes material, often energy, existing in discrete (specific) set of values (magnitudes or quantities).
Quantum mechanics	Description of phenomena in which particles have wave-like properties. The properties of atoms and energy are redefined in terms of wave functions.
Region	A specific area or section.
Relative probability	The ratio of the probability of finding a particle in one region with respect to another region.
Resin	A hard, transparent, and durable plastic. It is used in LEDs to protect the circuit from physical damage.
Resistance (electrical)	An opposition to the flow of electrical current characteristic of a circuit element. It is defined as the ratio of voltage (Volts) to current (Amperes). It is measured in Ohms or Volts/Amperes.
Resistor	An electrical device that provides a specific amount of electrical resistance to the passage of electrical current. This device obeys Ohm's Law.
Resonance	A phenomena in which an objects oscillations are driven at its natural frequency by vibrations from another source..
Scanning Tunneling Microscope (STM)	An instrument consisting of an extremely fine metal tip that is moved over the surface of a sample to generate an image of an extremely small object (one nanometer or smaller).
Sine wave	The waveform created from plotting the sine of an angle versus the angle.
Solar Cell	A semiconductor diode that absorbs light and generates a current. The generation of current occurs when electrons, released from their atoms due to the light, cross the P-N junction.
Solid	States of matter that have fixed shapes and volumes.
Solid-state	Electronic devices that use semiconductor materials.
Sonoluminescence	Describes light emission that occurs in bubbles exposed to sound (audible to ultrasonic).
Spectra	The display of the component colors of a light source.
Spectral line	A particular wavelength(s) of light emitted or absorbed by an atom or molecule.
Spectroscope	An instrument for examining the different wavelengths in a spectrum.
Spectrum	A range of electromagnetic radiation emitted or absorbed by a substance.
Speed	Distance traveled in unit time.
Speed of the chemical reaction	Rate of association or disassociation of chemicals that are reacting.
Squid	A deep-sea invertebrate, characterized by 10 arms, that emits bioluminescent light.
Standing wave	The interference effect from two waves of the same type moving with the same frequency in the same medium.
Sterilization lamp	A device used for killing microorganisms by exposing them to ultraviolet (uv) light.
STM (scanning tunneling microscope)	An instrument consisting of an extremely fine metal tip that is moved over the surface of a sample to generate an image of an extremely small object (one nanometer or smaller).
Subatomic	Indivisible particles from which all matter is formed.
Subspace	In science fiction, a region of space where energy can be transported at speeds faster than light.
Temperature	A measure of the heat contained in a body.
Thermoluminescence	Light emission produced by an object when its temperature is raised.
Transition	The process of an object emitting or absorbing energy. During a transition of an electron in an atom, energy is emitted or absorbed.
Transmission	Describes a wave packet that is incident on a potential barrier and has an energy less than the barrier height. The probability that it tunnels through the barrier and appears on the other side is non-zero. It is like a bullet, piercing a hole through a wall and emerging on the other side.
Triboluminescence	Light emission caused by adding mechanical energy to a material.
Tungsten	(W) A white or gray metallic transition element. It is used in various alloys, especially in lamp filaments.
Tunnel diode	A semiconductor device in which quantum tunneling is the reason that current moves.
Tunneling	A quantum mechanical phenomenon that predicts that a particle (or wave function representing it) incident on one side of a potential barrier has a finite probability of appearing on the other side although its total energy is less than the highest potential energy of the barrier.
Tunneling current	The current created by particles that undergo quantum tunneling.
Tunneling probability	The probability that quantum tunneling will occur. It is the square of the ratio of the amplitude of the wave function on the transmitted side of the barrier to that of the amplitude on the incident side.
Turning point	Locations where the total energy of an object equals its potential energy. In classical physics, objects change their direction of motion at these locations.
Ultraviolet (uv)	A form of electromagnetic radiation shorter in wavelength than visible light. Ultraviolet (uv) wavelengths range between about 1 nm and 400 nm.
Uncertainty	The degree of the lack of knowledge in the value of a measured quantity
Uranium	A radioactive element. It displays phosphorescence and trace amounts can be found in carnival glass and other common objects.
Vacuum	A space which contains no matter.
Valence band	An energy band where electrons do not have sufficient energy to break free from their respective atoms and hence do not conduct electricity. These electrons are tied to the respective atoms.
Valence band edge (Ev)	The highest energy level in the valence band.
Voltage	Electric potential difference measured in volts.
Voltmeter	A meter used to measure electrical voltage.
Volts	The SI unit of electric potential difference (Joule/Coulomb).
Wave	A method of energy transfer involving some form of vibration but no net motion of matter.
Wave function	In quantum mechanics the mathematical or graphical function which is used to describe the motion of an object. The square of the wave function is related to the probability of finding an object at a location.
Wave packet	A wave function for an individual object which is located in a relatively small region of space.
Wavelength	The distance in space over which the wave executes one cycle of its basic repeated form.
X-rays	Radiation due to the rapid deceleration of high-speed, charged particles.