Appendix A

Glossary

A Aberration:

In microscopy, an effect that causes distortion or blurring of the image. Aberration, Chromatic:

An effect created by the dispersion of the material from which the lens is made. This causes different wavelengths of light to be refracted to different de-grees. The name chromatic comes from the colors evident with this type of aber-ration. Aberration, Spherical:

An aberration caused by a lens being spherical. Spherical aberration is char-acterized by the edges of the image being magnified more than the center. Re-moved by using an aspheric lens or multiple spherical lenses. Achromat doublet:

Two lenses of different refractive indices placed next to each other to elimi-nate chromatic aberration in a lens system. See chromatic aberration.

Accommodate:

In ophthalmology, to focus by contracting the crystalline lens of the eye.

Alpha, α: Greek symbol used to denote an alpha particle.

Alpha Particle: A doubly charged positive helium ion consisting of two protons and two neu-

trons. A term usually used in conjunction with radiation. Alpha particles can be ejected from certain radioactive isotopes.

166 Appendix A

Amplitude:

The measure of a wave from its lowest point to its highest. In physical mani-festations of waves, such as in water, the amplitude is a measure of distance. With light, the amplitude is a measure of the wave’s energy. Angstrom:

1 x 10-10 m. A convenient unit of measurement, as atom diameters are on the order of angstroms. Represented by the symbol Å. Antisolar point:

The point 180˚ from the Sun, relative to an observer. The angular measure of rainbows can be made from the antisolar point, which corresponds to the shadow of one’s head.

Anti-twilight arch:

The band of light above the horizon opposite a rising or setting sun. This phenomenon is due to an optical mix of Rayleigh-scattered blue wavelength light, and red wavelength light reflected from larger particles in the atmosphere. See Rayleigh scattering.

Aperture:

A small hole through which light passes. Apertures are used to form images or mask undesired light from an image. Aqueous humor:

Liquid inside the cornea of the eye with a refractive index of 1.376.

Aragonite: One of the two crystal forms of calcium carbonate, the other being calcite.

Calcite is normally the stable phase. Both are present in the shells of certain sea creatures. Atom:

The smallest particle of an element, which cannot be subdivided without cre-ating another element. Atoms have nuclei consisting of positively charged pro-tons and neutrons, which are not charged. The nucleus is surrounded by nega-tively charged electrons. Together, they make the atom neutrally charged. Almost all of the mass of an atom is in the nucleus.

Glossary 167

The number of protons in an atomic nucleus. For a neutral atom, this also cor-responds to the number of electrons orbiting the nucleus. For example, carbon, with symbol C on the periodic chart, has an atomic number of 6. This means that it has 6 protons, and the neutral carbon atom has 6 electrons.

Attenuation:

Weakening in force or intensity: “attenuation in the volume of sound.” B

Beta, β:

Greek symbol used to denote electrons.

Beta Particles: High-energy electrons.

Bremsstrahlung Radiation: An electric charge, as it is being accelerated or decelerated, produces radia-

tion, which can be in the form of x-rays. This radiation is called Bremsstrahlung Radiation and usually creates an unwanted background in a spectrum.

C

Camera Obscura:

A room or box containing a hole in at least one of the walls that creates an image of the outside objects on the opposite wall.

Cantilever:

A projecting structure, such as a beam, that is supported at one end and car-ries a load at the other end or along its length.

Cathode-Ray Tube:

A vacuum tube in which cathode rays, in the form of a slender beam of elec-trons, are projected on a fluorescent screen and produce a luminous spot.

Charged:

Having acquired a net electric charge. Objects can become charged due to a transfer of electrons from one object to another. An example of this transfer is that which occurs while shuffling across a carpet or the rubbing of a plastic rod with a piece of fur.

Atomic Number:

168 Appendix A

A substance consisting of atoms of different atomic numbers. Compton Scattering:

The change in direction and energy of a photon due to the interaction with an electron.

Compound Microscope:

A microscope containing at least two lenses to form the image of a specimen. Invented by Robert Hooke in the mid-seventeenth century.

Concave:

An inward curvature. A concave lens or mirror has at least one surface that curves inward. A concave lens causes light rays to diverge, and a concave mirror causes light rays to converge. A mnemonic device to remember the difference between concave and convex is that caves are concave. Cones:

The photosensitive cells in the eye’s retina that respond to changes in the en-ergy, or wavelength, of light. There are three types of cones: red-sensitive, blue-sensitive, and green-sensitive.

Converge:

To come together or come to a single place or point. Convex:

An outward curvature. A convex mirror curves outward and a convex lens has at least one side that curves outward. A convex lens causes light rays to con-verge and a convex mirror causes light rays to diverge. Cornea:

The outer layer of the eye. A major contributor to the refraction of light in the eye.

Coulomb:

A unit of electric charge. 6.25 x 1018 electrons will have a charge of one cou-lomb. A Coulomb per second flowing through a wire is defined as one Ampere. Count:

The electronic pulse created in a detector by one quantum of radiation. Counts are summed to make spectral peaks.

Compound:

169

The angle beyond which light, traveling through an optically dense medium and incident on the interface with a less dense medium, will totally internally re-flect. For light exiting glass to air, the critical angle is 41˚. See total internal re-flection.

Crystal:

A regular arrangement of atoms in three-dimensional space. Sometimes this regular arrangement gives the crystal a definite three-dimensional shape. For ex-ample, if the atoms arrange themselves in a cubic lattice, the crystal might be cubic.

Crystalline Lens:

The lens inside a human eye. D

Depth of Focus:

Same as depth of field. Depth of Field:

The spatial depth over which features can be considered in focus. The dis-tance along the optic axis over which features are in focus. Detector (Radiation):

Any device that detects incoming radiation and can create an electronic signal for every quantum of radiation, proportional to the energy of the quantum. De-tectors can be of many types, gas and solid state. However, the detectors referred to here are all solid state, usually lithium drifted silicon. Diffraction:

The bending of waves around corners. Sound can diffract around buildings and light can diffract around very small obstacles. The obstacle must be of a size similar to or smaller than the length of the wave involved. Diffraction can lead to interference phenomena. Diffraction Grating:

A device which uses diffraction and interference phenomena to disperse a beam of light into its various wavelengths.

Diode:

A semiconductor device that emits light or can produce power when used as a solar cell.

Glossary

Critical angle:

170 Appendix A

Diopters: A unit of measurement used in optometry. A diopter is the inverse of a lens’

focal length, measured in meters.

Dispersion: The change in refractive index with wavelength. Most refractive materials re-

fract short wavelengths of light more than long wavelengths of light. This prop-erty is called the dispersion of the medium. Diverge:

To spread or move apart. Dopant:

A substance mixed in exceedingly small quantities with an otherwise pure substance. For example, phosphorus atoms are dopants in the semiconductor silicon.

E

Earth’s Shadow:

The shadow of the Earth projected onto the atmosphere. Often seen for sev-eral minutes in a clear sky after sunset. The shadow is low on the horizon, bluish in color, and rises as the sun sets lower beyond the western horizon.

Eclipse:

A shadow or the act of blocking light. In astronomy, it refers to the phenome-non of the Moon blocking the Sun’s light (solar eclipse), or the Earth blocking the Sun’s light to the Moon (lunar eclipse).

Elastic Collision: A collision between two bodies during which kinetic energy is conserved. During an elastic collision the bodies do not stay together. Electromagnetic Radiation:

The type of radiation we know as light: x-rays, radio waves, ultraviolet and infrared, among others. Electromagnetic radiation consists of alternating elec-tronic and magnetic fields at right angles to each other. Both of these fields con-sist of waves and impart electromagnetic radiation with a specific wavelength and frequency. Electromagnetic radiation travels at 3 x 108 meters per second in a vacuum. See electromagnetic spectrum.

171

The entire range of wavelengths through which electromagnetic radiation can be manifested. The longest wavelengths are the lowest energies and the shortest wavelengths are the highest. Starting at the longest wavelengths, there are radio waves, which proceed through the microwave region. The next highest energy radiation is infrared followed by visible light, then ultraviolet radiation, x-rays and then gamma rays. Electron:

An elementary particle having a rest mass of 9.11 x 10-31 kilograms and an electric charge of -1.602 x 10-19 coulombs. Electrons, being negatively charged, cancel out the positive charge of an atoms nucleus. In the structure of an atom, electrons surround the positively charged nucleus.

Electron, Auger:

An electron that has been ejected from an atom by the Auger process. In this process, an inner shell electron is emitted from an atom. An outer shell electron then fills the inner shell vacancy, and in the process, the extra energy causes an-other outer shell electron to be ejected. This outer shell electron is referred to as the Auger electron and the energy of this electron is measured to determine ele-mental composition. Electron, Backscattered:

An electron that has been scattered directly from a nucleus. Backscattered electrons lose very little energy as a result of the backscattering process and are usually used for compositional or Z contrast imaging in electron microscopy.

Electron, Secondary:

An electron that has been ejected from a sample as a result of bombardment by an incident beam, They are ejected only after considerable scattering and en-ergy loss inside the material. Secondary electrons are used for topographic imag-ing in electron microscopy. Electron Volt:

A unit of energy. An electron volt is equivalent to the energy required move an electron through a potential difference of one volt. An electron volt is equal to 1.602 x 10-19 joules. Element:

A substance consisting of atoms all of the same atomic number. Elements can combine to make compounds. Energy:

Glossary

Electromagnetic Spectrum:

172 Appendix A

A physical quantity defined as the ability to do work. Some of the types of energy include heat (the motion of atoms), kinetic (the movement of a mass through space), potential (a mass with the capability to move in response to a force), electrical, chemical, and others. Energy can be transformed from one form to another but not destroyed. Light is defined as electromagnetic energy.

Extended source:

A light source that emits from a finite area or volume. The Sun is an extended light source as seen in the sky. See point source.

F

First surface:

The surface of a lens or mirror that first encounters incident light. A house-hold mirror has a first surface of glass over a layer of silver.

Fluorescence:

An ability that some transparent bodies have to modify incident light to pro-duce light lower in energy and different in color from the mass of the material. For example, the hyaline layer is a glassy translucent material found in scorpi-ons that causes fluorescence under ultraviolet light.

Focal Length:

The distance from a lens at which parallel rays converge after they pass through the lens or reflect from a mirror.

Focal Plane:

The plane at which a lens forms images. A movie screen is at the focal plane of a projector’s lens.

Focal Point:

A point of convergence of parallel rays of light (or other radiation) or a point from which it diverges. The location at which rays parallel to the optical axis of an ideal mirror or lens converge to a point.

Frequency:

The number of waves passing a point in time. For light, this is usually ex-pressed in Hertz (Hz), the number of waves per second. Related to wavelength by the equation f = v/λ where f is the frequency, v is the wave velocity, and λ is the wavelength.

173

A lens in which only the outer layer of glass or plastic is used to refract light. Used in lighthouses, lanterns, and as flat lenses.

G

Gamma, γ:

Greek symbol used to denote high-energy photons. Gamma Radiation:

High-energy electromagnetic radiation emitted by excited atomic nuclei.

Gauss: A unit of magnetic field strength.

Grazing Incidence:

An object or light striking a surface at a highly oblique angle. Light encoun-tering a surface at grazing incidence is nearly 100% reflected. H Hole:

A vacancy in the electron population of a semiconductor, which acts as a positively charged current carrier.

Hooke’s Law:

An explanation of how springs behave. By applying force (F) to the spring, the spring will stretch by length (x). When you double the force (F) you double the length (x). Hooke’s law applies to both stretchable springs and compressible springs. The only limit is when the spring is stretched beyond its elasticity and becomes deformed.

Hyperopia:

A malady of the eye in which the focal plane rests behind the retina. Com-monly known as “farsightedness.” Corrected with convex lenses. I

Incandescence:

Giving off light due to the attainment of an extremely high temperature.

Glossary

Fresnel Lens:

174 Appendix A

See incandescence. Incident:

Describes electromagnetic energy or ions which are directed at and strike a target or sample. As opposed to scattered or reflected energy or particles, which are leaving the target or sample. Incident photons or other particles can be scat-tered, reflected, or absorbed. Index of Refraction:

See refractive index. Inelastic Collision:

A collision between two bodies in which kinetic energy is not conserved, but momentum is.

Infrared:

Radiation in the electromagnetic spectrum between visible light and radio waves.

Interface:

The boundary between two different materials or media. Interference:

The constructive and destructive addition of waves. Interference can lead to patterns sometimes called diffraction patterns, as in Young’s double slit experi-ment. Ion:

In general, any charged particle. In aqueous chemistry, usually a soluble charged particle. In physics, usually an atom with an electron added or removed. If an electron is added the ion is negatively charged; if an electron is removed, the ion is positively charged. When this happens, the atom is said to be ionized. Ionization:

The creation of ions. In physics, the gain or loss of an electron by an atom. In chemistry, the gain or loss of an electron by a group of atoms. Gaining an elec-tron creates a negative ion and losing an electron creates a positive ion. Iridescence:

The property of producing colors due to the interference effects of light re-flecting off of different layers at different angles. See interference.

Incandescent:

175

The network of muscle tissue in the eye that opens and closes the pupil and is responsible for the color of one’s eyes. See pupil.

Irradiate:

To expose to any type of radiation. Isotope:

A different form of the same element. Isotopes cannot differ in the number of protons or electrons they possess, but they do differ in the number of neutrons in the nucleus. See radioisotope.

J

Joule:

A unit of energy. The amount of energy it takes to exert a force of one New-ton through a distance of one meter. Also equal to one Watt of electrical energy expended for one second. See Newton.

K

Keratin: A protein which makes up most of the structure of hair and fingernails. L

Lambda, λ:

Greek symbol used to denote wavelength.

Laser: A device that utilizes the stimulated emission of light to create and amplify a

beam of light. The laser-producing material is often gallium arsenide, helium-neon, or ruby.

Lattice:

An imaginary regular arrangement of points in three-dimensional space. Most solids can be characterized by their lattice structures.

Lattice Point:

An imaginary point in three-dimensional space that defines a structure point of a lattice. Any lattice point is equal to any other lattice point. It will have the same number of lattice points around it in the same directions the same distance away as any other lattice point.

Glossary

Iris:

176 Appendix A

LED: Light emitting diode. A semiconductor device that emits light of a specific

energy when electrical current flows through it.

Lepton: Any of a class of elementary particles that consist of the electron, neutrino,

muon, and tau particle. M

Magnification:

The degree to which an image is larger than the object. Calculated as (image length) / (object length).

Meter:

A unit of length defined in 1800 as one ten-millionth of the meridian distance from the equator to the North Pole. One meter, symbol m, is approximately 39 inches in length.

Meteor:

The streak of light in the sky resulting from the incandescent particles given off by an incoming piece of space debris. Before it strikes the ground, the debris itself is called a meteoroid. After it has struck the ground, it is called a meteorite. Meteorite:

An object from space which has entered the Earths atmosphere and struck the ground. Meteorites can be “finds” or “falls”. Finds are found some unknown time after striking the Earth, and are not seen to strike the ground. Falls are seen to fall to the Earth and then are recovered where they were seen to fall.

Micro:

The Greek symbol µ, which denotes 10-6. Microbiology:

The study of microscopic organisms and single cells. Micron:

1 x 10-6 m. Symbol µm. Microscope:

An arrangement of lenses deigned to view objects at high magnification. A simple microscope contains only one lens. A compound microscope contains more than one lens. Electron microscopes contain electron lenses. By extension,

177

any device designed to view objects at larger magnification, even without lenses. (i.e., Scanning Tunneling Microscope, STM, Near Field Scanning Opti-cal Microscope, NSOM.) Mirage:

An image distorted by light refracted through heated or cooled air. Inferior mirages are formed in layers of cool air over warm air and are often seen in the desert. Superior mirages are formed in layers of warm air over cool air and are often seen over the ocean or frozen landscapes.

Molecule:

The smallest particle of a substance that retains the chemical and physical properties of the substance and is composed of two or more atoms; a group of like or different atoms held together by chemical forces.

Momentum:

That property which is conserved during elastic or inelastic collisions. It is defined as the product of the mass and the velocity of the body, and is repre-sented by p. p = m*v. Also equal to a force over a unit time. P = f*Δt. In quan-tum mechanics, p = h/λ where h is Planck’s constant and λ is wavelength. Mylar:

A trademark used for a thin, strong polyester film.

Myopia: A malady of the eye in which the focal plane rests in front of the retina.

Commonly known as “nearsightedness.” Corrected with concave lenses. N

Nanometer:

1 x 10-9 meters. Symbol nm. Neutron:

An elementary particle having mass 1.675 x 10-27 kg, slightly greater than that of the proton, and no charge. The nuclei of atoms contain protons and neutrons. Newton:

A unit of force in the M.K.S. system. The force required to impart to a mass of one kilogram an acceleration of one meter per second squared.

Glossary

178 Appendix A

Perpendicular, or at a right angle. Lines can be normal or perpendicular, planes can be normal, and lines can be normal to planes. Nucleus:

The very small positively charged core of an atom. The atomic nucleus con-sists of positively charged protons and uncharged neutrons. Most of the mass of an atom is in the nucleus.

O

Ommatidium:

A single unit in the compound eye of an insect. It consists of a facet, a lens and a photoreceptor. Opaque:

The property of blocking light. An opaque object passes no light through it. P

Penumbra:

The part of a shadow where some of the light from an extended light source is blocked. In astronomy, the penumbra is the area on the ground where observers see a partial solar eclipse. See umbra, eclipse.

Period:

The time to complete one cycle of motion. The period of the Earth’s rotation is 24 hours.

Phosphor:

A material that emits lower energy light when illuminated by high energy light. The insides of fluorescent light bulbs are coated with phosphor.

Photon:

A quantum of electromagnetic radiation. Photons are characteristic of all electromagnetic radiation, from the longest radio waves up to the shortest gamma rays. The shorter the wavelength of the radiation, the more energetic the photon is.

Piezoelectric effect:

Certain crystals with asymmetric unit cells have this property. When a com-pressive stress is applied to these crystals, it effectively shifts the positive ions in one direction and the negative ions in the other. This produces a temporary charge buildup on the opposite surfaces of the crystal. A tensile stress reverses

Normal:

179

the charge. The corollary effect can occur; an applied potential difference can change the shape of the crystal, or apply a force against a restraint.

Piezoelectricity:

Electricity or electric polarity due to pressure especially in a crystalline sub-stance (as quartz).

Pigment:

A substance used as coloring. Dry coloring matter, usually an insoluble pow-der, to be mixed with water, oil, or another base to produce paint and similar products.

Pinhole Camera:

A device used to record or view images of light caused by a pinhole that forces light rays to cross.

PIXE:

Particle Induced X-ray Emission. The process whereby an incident ion causes an inner shell electron to be ejected from an atom. The resulting electron transi-tion causes a characteristic x-ray, which is analyzed. Planck’s Constant:

A constant of proportionality between the wavelength of electromagnetic ra-diation and the energy by the equation E = h*c/λ. Where E is the energy of the photon of electromagnetic radiation, λ is the wavelength, c is the velocity of light and h is Planck’s constant, 6.626 x 10-34 Joule-seconds. Point Source:

An ideal light source that emits from an infinitesimally small area. Stars as seen in the sky are essentially point sources. See extended source.

Polarize:

To cause radiation to be polarized. If light passes through a polarizing filter, the alternating electric and magnetic fields will no longer be oriented in all di-rections perpendicular to the direction of motion, but will be oriented more strongly in specific directions. Light can also be polarized by passage through the atmosphere and by reflecting off of surfaces at a very shallow angle. See electromagnetic radiation. Positron:

Positively charged particles with the same mass as an electron.

Glossary

180 Appendix A

A malady of the eye in which the crystalline lens loses the ability to focus properly. Occurs commonly with age. Corrected with convex lenses.

Primary rainbow:

The rainbow found 40–42˚ from the antisolar point. Usually the only rainbow in the sky. Sometimes seen with the secondary rainbow.

Prism:

A device which uses the dispersion property of glass to split light into its component wavelengths.

Proton:

An elementary particle of mass 1.673 x 10-27 kg or about 1,836 times that of an electron. The proton has a charge equal in magnitude as that of an electron only it is positive instead of negative, being +1.602 x 10-19 Coulombs. The nu-clei of atoms contain protons and neutrons.

Probe:

A usually small object used especially for exploration to obtain specific in-formation. Definition created in 1580.

Pupil:

The aperture of the eye. See iris. Q

Quantum:

A discrete unit that exists at very small dimensions. A quantum of electro-magnetic energy (light) is the photon.

R

Radiation:

The emission of particles from a source. The particles may have mass, as in the case of neutrons or alpha particles, or they may be massless as in the case of photons such as x-rays and gamma rays. Radioisotope:

A different form of a radioactive element that emits radiation. The radioiso-tope differs in the number of neutrons in the nucleus of an atom.

Presbyopia:

181

A scan pattern (as of the electron beam in a cathode-ray tube) in which an area is scanned from side to side in line from top to bottom; also: a pattern of closely spaced rows of dots that form the image on cathode-ray tube (as of a television or computer display). Rayleigh Scattering:

The scattering of light or electrons due to interactions with particles whose size roughly corresponds to the wavelength of the photons or electrons. The amount of scattering follows the inverse of the wavelength to the fourth power. Blue sky, smoke, and some animal coloring are due to Rayleigh scattering.

Reflection:

The act of striking a surface and being repelled from it. When an incident photon leaves a surface on the same side (as opposed to the opposite side, being transmitted, or being absorbed in the material) it has been reflected. Different surfaces reflect light to different degrees and different surfaces reflect different wavelengths of light. For example, if a surface reflects light of 4,500 Angstroms, we say it reflects blue light. Refraction:

The act of passing through a transparent material and changing direction at the interface. The degree to which light refracts at an interface is determined by Snell’s law.

Refractive Index:

A numerical measure of refraction, related to the velocity of light in a mate-rial. Denoted by the letter n. n = v0/vn, where v0 is the velocity of light in a vac-uum, and vn is the velocity of light in the medium of refractive index n. n in a vacuum is 1, while n in water is 1.33. See refraction.

Resolve:

The ability to discern two separate, closely spaced objects. Related to resolv-ing power, the ability of a device to optically resolve distinct objects.

Retina:

The layer of photosensitive cells at the rear of the human eye.

Rods: The photosensitive cells in the eye’s retina that respond to changes in the

brightness of light.

Glossary

Raster:

182 Appendix A

Secondary Rainbow: The rainbow seen outside a primary rainbow. This rainbow is 49-51˚ from

the antisolar point, and its colors are reversed relative to the primary.

Selection Rules: In x-ray emission from atoms, these rules determine which electron transi-

tions between energy states are allowed.

SEM-EDS: Scanning Electron Microscopy-Energy Dispersive Spectroscopy. The process

whereby an incident electron causes an inner shell electron to be ejected from an atom. The resulting electron transition causes a characteristic x-ray, which is analyzed. This takes place in an electron microscope as the electrons used for imaging also cause the emission of x-rays. Semiconductor:

A material that can be an insulator in very pure form, but is usually doped with very small amounts of impurities in order to cause it to conduct with more or less resistance depending on the amount of the dopant. Silicon and germa-nium are two elemental semiconductors. Unlike a metal, the resistance of a semiconductor decreases with an increase in temperature. Solar Cell:

A semiconductor device used to produce power when irradiated by sunlight.

Sound: Vibrations of air molecules that we hear.

Spectrometer: An instrument used for measuring the energies and wavelengths of photons.

Spectroscope: An optical instrument that produces a spectrum of the wavelengths of light.

Spectrum: Plural, Spectra. Any visible manifestation of radiation, which is arranged ac-

cording to wavelength or energy. Can refer to the visible spread of radiation caused by a prism or diffraction grating in visible light, or to the graph created by any method of plotting radiation intensity versus photon energy or wave-length.

S

183

The speed at which electromagnetic energy travels in a vacuum, which is 3 x 108 m/s. Nothing that carries information can travel faster than the speed of light.

Sundog:

An atmospheric optical phenomenon that mimics the image of the Sun. Caused by light refracting through horizontal ice crystals in the atmosphere, which often disperse the light as well. Also known as parhelia, sundogs are found 22˚ from the solar disk in skies with cirrus clouds.

T

Total Internal Reflection:

A phenomenon that occurs when light is incident on an interface between two media of different refractive indices. If the light is traveling through a denser medium and strikes the surface at an angle greater than the critical angle, the light will be totally reflected inside the medium. Optical fibers take advantage of this property to propagate light through the fiber.

Translucent:

The property of passing light with some loss of the light. One can normally see part way into translucent objects, but not all the way through. Transparent:

The property of passing light.

U Ultraviolet:

A region of the electromagnetic spectrum in which the photons have higher energy than the visible region but lower energy than x-rays. Opinions vary on exactly where the ultraviolet region begins and ends, but the wavelengths are about 100 angstroms to about 4000 angstroms.

Umbra:

The central part of a shadow where all light from an extended (or point) source is blocked. See penumbra, eclipse

Unimpeded:

Not slowed or prevented; a good vacuum is necessary to allow the electrons to move unimpeded down the column of a scanning electron microscope.

Glossary

Speed of Light:

184 Appendix A

V Vacuum:

A condition of rarified gas. A perfect vacuum can never be attained, as every surface has water and various other substances on it in minute quantities, which will evaporate under conditions of vacuum.

Visual Ray:

Theorized by Empedocles in the fifth century BC to explain the visual per-ception. An human eye would emit a visual ray to intercept a light ray from an object; the returning ray combination would inform the observer of the per-ceived object.

W

Wave Number:

The number of waves in a given length. Equal to the reciprocal of the wave-length, 1/λ. Wavelength:

The distance between two successive peaks or troughs on a wave. Related to frequency by the equation f = v/λ, where f is the frequency, v is the velocity of the wave and λ is the wavelength.

X X-ray:

Any quantum of electromagnetic radiation between the wavelengths of 1 x 10-9 m and 1 x 10-11 m or between the energies of approximately 1 keV and approximately 100 keV. X-ray Diffraction:

The reflection of x-rays from planes of atoms.

XRF: X-Ray Fluorescence. The process whereby an incident photon causes an in-

ner-shell electron to be ejected from an atom. The resulting electron transition causes a characteristic x-ray, which is a signature for and identifies the atom.

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fo/english/mirage.html Pedrotti FL, Pedrotti L (1993) Introduction to optics. Prentice Hall, New Jersey. Perkowitz S (1996) Empire of light. Henry Holt and Company, New York Ritter, JW (1801) Naturforschende Gesellschaft Zu Jena. Roche S, Courage G, Devinoy, P (1985) Mirrors. Rizzoli, New York. Rontgen WC (1896) On a new kind of rays. Nature. 53:274 Rossing TD, Chiaverina, CJ (1999) Light science: Science and visual arts. Springer-

Verlag, New York. Rossotti H (1983) Colour. Princeton University Press, Princeton Sabra AI (1981) Theories of light: From Descartes to Newton. Cambridge University

Press, Cambridge Simon H (1971) The splendor of iridescence. Dodd, Mead and Company, New York Sobel D (1995) Longitude. Walker & Co., New York Sobel MI (1987) Light. University of Chicago Press, Chicago Spiro IJ, Schlessinger M (1989) Infrared technology fundamentals. Marcel Dekker, Inc.,

New York Steadman P (2001) Vermeer’s camera. Oxford University Press, Oxford. Taft WS, Mayer JW (2000) The science of paintings. Springer-Verlag, New York Thompson JJ (1897) Philosophical Magazine 44:293

Index

aberration, 67, 68

chromatic. See chromatic aberration circle of confusion, 68 spherical. See spherical aberration

accelerators, 162 accommodating, 70 achromat doublet, 69 air-cornea interface, 70 alpenglow, 125 Alpha Proton X-ray Spectrometer, 162 amplitude, 38 analyzer, 136 angle of incidence, 35, 45

rainbow, 104, 113 angle of refraction, 35, 44 antisolar line

rainbow, 108, 113 antisolar point, 106 anti-twilight arch, 125 aperture, 10 Apollo mission, 157 APXS. See Alpha Proton X-ray

Spectrometer aqueous humor. See eye art, 154 asphaltum, 25

Bartholine, Erasmus

two-beam effect, 137 beamline

external, 162 Becquerel, Henri

phosphorescence, 140 binding energy, 145, 158 black light, 153 blue light, 115, 118, 125 Bohr Model, 142, 143

Planck's constant, 142 potential well, 142

Bohr, Niels, 142, See also Bohr Model Brewster angle, 134 Bunsen, Robert, 144 burning glasses, 54, 55

calcite crystal, 137

illustration, 137 calotype. See photograph camera obscura, 10, 11 cataracts. See vision problems cathode rays, 141 CCD. See charge-coupled devices characteristic x-ray, 146, 158

line spectra, 146 charge-coupled devices, 58

in astronomy, 58 chemical analysis, 160 chromatic aberration, 57

achromat doublet, 69 correction of, 69 diagram of, 68

circular polarization, 133 cloud

contrail, 120 gray, 119 white, 119

coating antireflection, 96

coherent light, 95 color

blue object, 82 circle diagram, 79 cones, 90 film thickness, 96 Newton, Isaac. See Newton, Isaac of clouds. See cloud

188 Index

of smoke, 118 of the sea, 116 of the sky, 115 perception, 90 perception of, 89 prism. See prism smoke when inhaled, 119 spectrum, 75 visible spectrum, 80 wavelength, 80

color blindness. See vision problems compound lens

diagram, 58 compound microscope, 57

charge-coupled devices, 57 Drum Optical Microscope, 58 eyepiece, 57 objective lens, 57

concave mirror, 19, 20, 21 condensation, 119 cone of color, 110 conjunctiva. See eye contrail, 120 convex mirror, 19, 20, 21, 22 Copernicus, 66 cornea. See eye corpuscles, 36 Crocker Land. See mirage crystalline lens, 10, See eye, See eye

Daguerre, Louis Jacques Mande, 25,

26, 27, 28 daguerreotype, 26, 27

development process, 29 negative image, 32 positive image, 28, 32 resolution, 29 specular reflection, 30, 31

depth of focus, 53, 60 optical microscope, 60 Scanning Electron Microscope, 60,

64 Descartes, René

Law of Refraction, 42 dewar

Scanning Electron Microscope, 146 diamond, 36, 43 diffraction, 46, 91, 100

gratings, 101 diffuse reflection, 23, 29 diopter, 52 dispersion, 68, 103 diverging lens, 50 double refraction

wave theory, 138

Einstein, Albert, 38, 80 photons, 80 quantum theory, 140

electricity magnetic fields, 141

electromagnetic radiation, 77 as sunlight, 84

electromagnetic spectrum diagram of, 78, 81 gamma rays, 78 infrared, 139 photon, 81 radio waves, 78 ultraviolet, 139 wavelength, 81 x-ray, 139

electromagnetic theory, 77 electron

band, 158 Becquerel, Henri, 140 binding energy, 145 cathode rays, 141 deflection, 141 energies, 142 energy levels, 142, 158 kinetic energy, 142 light absorption, 152 Millikan, Robert, 141 orbitals, 142 plum pudding, 141 properties of, 140 spontaneous emission, 141

electron gun. See Scanning Electron Microscope

electron volt, 80 Empedocles, 13 Energy Dispersive Spectroscope, 160 Euclid, 13, 15 external beamline, 162 eye, 69, See also vision problems

Index 189

accommodating, 70 aqueous humor, 69 as a lens, 69 color perception, 89 conjunctiva, 69, 70 cornea, 69 crystalline lens, 70 diagram of, 71 focal length, 71 iris, 70 iris color, 118 photoreceptors, 80 polarization, 138 pupil, 70 retina, 70, 89 vitreous humor, 70

Faraday, Michael, 38 electromagnetic nature of light, 141

farsightedness. See vision problems film

interference, 96 oil, 96 thickness, 96

first surface, 17 fluorescence, 85, 153, 158

black light, 153 scorpion, 153 ultraviolet light, 153

focal length, 50 focal plane, 54 focal point, 19, 20, 21, 50 Foucault, Jean Bernard, 17 Fresnel, A.J., 38 fundamental constants, 4

Galileo

Copernicus, 66 telescope, 66

gamma rays, 78, 152 glacier glasses, 134 glare, 133 glass

secondary image, 18 grazing incidence, 18 Gregory, James

reflecting telescope, 17 ground state, 88

Haidinger’s brush, 138 Herschel, William

infrared, 148 Hooke, Robert, 37

inverted telescope, 57 Micrographia, 59

Hubble Space Telescope, 18, 19 NGC 3532, 67 primary mirror, 67

Huygens, Christiaan, 37 Huygen's Principle, 100 two-beam effect, 137

hydrogen. See also Bohr Model spectral lines, 142

hyperopia, 52

Iceland Spar, 136 image

focal point, 21 in a spoon, 22 polished, 22 real, 55 upside-down, 21 virtual, 55, 56

images upside down, 9

incident light, 35, 40, 44 index of refraction

Brewster angle, 134 infrared, 77, 80, 148

art, 154 photon, 154 reflectography, 154 space exploration, 156

interference, 91 colors, 95 constructive, 91 destructive, 96 diffraction. See diffraction iridescence, 99 oil slicks, 95 soap bubbles, 95 wave, 100

iridescence, 99 iris. See eye

Jupiter, 66

190 Index

Kepler, Johannes, 14

hanging image, 55 Kirchhoff, Gustav

spectrum, 144

laser, 81, 87 latent image, 25 Law of Equal Angles, 15, 16, 19, 22,

23 Euclid, 15

Law of Refraction, 42 Least Time

Pierre de Fermat, 2 Principle of, 2

Leeuwenhoek microscope, 56 water drop, 56

lens camera, 97 coatings, 96 concave, 52 converging. See convex lens convex, 52, 54 diopter, 52 diverging, 50 doublet lenses, 57 focal length, 50 focal point, 50 glass, 56 image side, 52 magnification, 55 negative. See concave lens object side, 52 plano-convex, 56 positive. See convex prescription, 50 resolution, 52 single, 56

light. See also polarization, See also light sources absorption, 152 as a wave, 91 as particles, 139 Brewster angle, 134 coherent, 95 diffraction, 46, 91 direction of, 35, 40 dispersion, 103

divergent, 50 dual nature of, 139 electromagnetic nature of, 141 extended sources of, 6 glare, 133 in diamond, 36 in glass, 40 in vacuum, 36 infrared, 77, 148 interface of materials, 7 interference effects, 93 interference illustration, 93 Newton, Isaac, 99 parallel, 50 particle, 80 path of, 33 point sources of, 6 prism, 75 radiative energy, 139 reflection, 133 refraction, 34 refractive index, 43 reversible path of, 7 spectrometer, 85 speed of, 3, 4, 12, 33 straight path of, 2 ultraviolet, 77, 149 velocity of, 35 visible, 75, 77 wave, 92, 132 waves, 36 white, 103 x-ray, 149

light interference Newton's Rings, 99

light sources fluorescent bulb, 85 future technology, 87 laser, 87 light-emitting diodes, 85 sun. See sun

light wave beach analogy, 40

line spectra, 146 linear polarization, 133 liquid nitrogen

spectrometers, 146 longitudinal, 132

Index 191

Lowell Observatory, 49 Lowell, Percival, 49

Mars, 66 luminiferous ether, 5 lunar soil, 157

magnetic fields

electricity, 141 Faraday, Michael, 141

magnification, 55 water-drop, 56

Mars thermal images, 156

Mars Global Surveyor, 156 Mars Pathfinder Mission, 162 matte, 23 Maxwell, James Clerk, 76

electric fields, 141 electromagnetic radiation, 77 electromagnetic theory, 77

megapixel, 58 mercury, 27, 28

fluorescent bulbs, 85 Michelson, Albert, 5, 17

luminiferous ether, 5 micrograph, 64 microscope

compound. See compound microscope

Leeuwenhoek, 56 optical versus electron, 64 single lens, 56

Millikan, Robert electron charge, 141 electron mass, 141

mirage, 129 Crocker Land, 128 superior, 128

mirror as warfare, 16 concave, 19, 21 convex, 19, 20, 21, 22 curved, 18 focal point, 21 grazing incidence, 18 Hubble Space Telescope, 18, 19 Law of Equal Angles, 19 plane, 16, 21

raindrop, 104 rotating, 17 secondary image, 18 spoon, 19

mirror-based telescope, 50 moon, 157

energetic particles, 157 moon enlargement syndrome, 126 moondogs. See paraselenae multiply reflected, 122 Musée Mechanique, 10

nanometers, 78 nearsightedness. See vision problems Newton, Isaac, 36, 37, 46, 75

circle of visible light, 79 corpuscles, 36 emissionists, 76, 93 light interference, 99 Newton's Rings, 99 Optiks, 76 telescope, 67 two-beam effect, 137

Newton’s Rings, 98, 99 Niepce, Nicephore, 25 normal, 15

objective lens

doublet lenses, 57 oblique angle, 18 oil slick, 96 Ole Roemer, 4 optical axis, 50 optical microscope

charge-coupled devices, 64 sample image, 65

painting. See art parallel

incident light rays, 23 paraselenae, 130 parhelia, 129 penumbra, 5, 6 phosphorescence, 153 phosphors, 85 photoelectric effect, 140 photograph

calotype, 25

192 Index

development, 27 first, 25 fixer. See sodium thiosulfate silver chloride, 27

photon, 140 absorption, 152, 154 Bohr Model, 142 coherent waves, 88 scattering, 85 velocity in vacuum, 142

photoreceptors, 90 pigment

in art, 154 pinhole camera, 8, 9, 10 PIXE. See x-ray pixel, 58 Planck’s constant, 142 plane mirror. See mirror Plato, 13 plum pudding, 141 polarization

absorption, 135 circular, 133 eye, 138 linear, 133 reflection, 133 scattering, 134 transverse, 132 vector notation, illustration, 133

polarized Brewster angle, 134 films, illustration, 131 glacier glasses, 134 Haidinger's brush, 138 horizontally, 135 human vision, 138 Isaac Newton, 132 light, 131 linear, 133 reflection, 136 sunglasses, 132 two-beam effect. See two-beam

effect vertically, 135

polarizer, 136 analyzer, 136

Polaroid, 135, 136 film, 135

potential well, 142 preferential scattering

alpenglow, 125 cloud. See cloud rock candy, 122 salt, 122 sea foam, 122 sunset, 123 volcanic eruptions, 124 water, 118

presbyopia, 72 primary rainbow, 110 prism, 75, 103

diagram of, 77 rainbow, 104 spectrometer, 144

proton, 142 pupil. See eye

quantum mechanics, 36

radiation

infrared, 148 light, 148 Ritter, J.W., 149 short, long wavelength, 80 ultraviolet, 149 x-ray, 149

radiative energy, 139 radio waves, 78 radiography. See x-ray rain band, 108 rain circle, 108 rainbow, 103

angle of incidence, 104, 113 antisolar line, 108, 113 antisolar point, 106 cone of color, 110, 114 dispersion, 103 early theories, 103 experiment, 103, 105 in mist, 114 index of refraction, 104 primary rainbow, 110 prism, 104 rain band, 108 rain circle, 108 reflected rays, 104

Index 193

refracted rays, 104 secondary rainbow, 110

raster, 63 Rayleigh scattering, 134 reflecting telescope

James Gregory, 17 reflection, 23, 34, 133

diffuse, 23, 115 Law of Equal Angles, 23 specular, 23, 115 total, internal, 45

reflectogram, 154 reflectography, 154 refraction, 34, 35, 125

atmospheric ice, 130 mirage, 127, 128 moondogs, 130 of the atmosphere, 125 rainbow, 103 refractive index, 125 sundogs, 129 sunset, 125

refraction of Light, 33 refractive index, 44, 125, 128

dispersion, 68 table of values, 43

resolution, 52 resolving power, 60, 64 retina. See eye Ritter, J.W., 149

ultraviolet radiation, 149 Röntgen, W.C., 149 Rutherford, Ernest, 141

Scanning Electron Microscope

chamber, 63 column, 63 cut-away diagram, 62 depth of focus, 60, 64 detector and monitor, 63 dewar, 146 disadvantages, 64 electromagnetic fields, 63 electron gun, 63 electrons, 62 lens system, 63 lenses, 62 raster, 63

resolving power, 60 sample image, 65 secondary electrons, 63 vacuum system, 63, 64 voltage, 63 x-ray spectrometer, 146

scattering, 134 scorpion, 153 secondary electrons, 63 secondary rainbow, 110 silver chloride (AgCl), 27 single lens

von Leeuwenhoek, Antony, 56 slits, 94 Snell, Willebrod van Royen

Law of Refraction, 42 soap bubbles, 95 sodium thiosulfate, 28 Sojourner Rover, 162 solar eclipse, 6, 7, 10 Space Telescope Institute, 67 spectra

Bohr Model, 142 spectral lines, 142 spectral signature, 78, 144 spectrometer, 85, 144

liquid nitrogen, 146 spectrum, 75

Bunsen, Robert, 144 Kirchhoff, Gustav, 144

specular reflection, 23, 30 speed of light, 3, 4, 5, 12

energy, relative to, 140 spherical aberration, 68 spoon, 19, 20, 22 star

spectral signature, 144 straight path of light, 2 sugar, 122 sun

gamma rays, 84 hydrogen, 84 light, 84 visible light, 83

Sun antisolar point, 106

sundogs. See parhelia sunglasses, 132

194 Index

glacier glasses, 134 human vision, 138 polarized, 132

Superman vision, 13 Surveyor, 156

Talbot, William Henry Fox, 25, 26, 27 telescope

Galileo, 66 reflecting, 67, See mirror-based refracting, 67 Very Large Telescope, 66 Yerkes, 66

TES. See Thermal Emission Spectrometer

Thermal Emission Spectrometer, 155 Thomson, J.J.

Cavendish Laboratory, 141 electron, 141

transverse, 132 two-beam effect

Bartholine, Erasmus, 137 calcite crystal, 137 Huygens, Christiaan, 137 Newton, Isaac, 137

Tyndall, John, 88 Tyndall structural color, 88

ultraviolet, 80, 84 light, 153 radiation, 149

umbra, 6

van Eyck, Jan, 11 Vermeer, Johannes, 11 Very Large Telescope (VLT), 66 Villard, Paul

gamma rays, 77 virtual image, 55 visible light, 75, 77 vision problems

cataracts, 70 color blindness, 73 farsightedness. See hyperopia hyperopia, 52, 72 myopia, 52, 71 nearsightedness. See myopia presbyopia, 72

refractive surgery, 73 volcanic eruptions, 124 von Leeuwenhoek, Antony

microscope, 56

water color of, 118 condensation, 119 contrails, 120 in smoke, 119 mirage, 127 preferential scattering, 118 scattering of light, 118 surface reflection, 118

wave, 132 amplitude, 38 diffraction, 91 energy, 38 frequency, 38 in phase, 91 interference, 91 light, 92 phase reversal, 95 polarized, 132 properties of, 38 speed, 38 theorists, 94 water, 92 wavelength, 38 Wavelength Dispersive

Spectroscope, 160 wave theorists, 43 wavelength, 78, 80 Wavelength Dispersive Spectroscope,

160 white light, 103 window glass, 152

x-ray, 149, See also characteristic x-ray

absorption, 149, 152 alpha transition, 158 atomic number, 158 beta transition, 158 characteristic, 158 chemical analysis, 160 Energy Dispersive Spectroscope,

160 fluorescence, 153, 158

Index 195

in art, 158 particle-induced emission (PIXE),

158, 162 photography, 150 radiography, 150 Röntgen, W.C., 149 Wavelength Dispersive

Spectroscope, 160

x-ray emission, 158

Yerkes Observatory, 49 Yogi Bear, 164 Young, Thomas, 37, 93

emissionists, 94 experiments, 94