APPENDIX AA Useful Information Just as you need to know your name and address and telephone number and e-mail address to locate yourself in the world, so must you know some basic information to locate yourself in physics. Like competent profession- als in any field, a practicing physicist carries a large amount of factual baggage. Starting out in physics you will need only the small backpack of facts presented in Tables A.1 and A.3. Then there is information that you need occasionally. Some of that is collected here for your convenience. If you don’t find what you want here or in the text, try the library. Ask a reference librarian to help you find what you want to know, or look in the Handbook of Chemistry and Physics. You can also use the World Wide Web to find constants: http://physics.nist.gov/cuu/Constants/index.html will supply you the very latest, most precise values from NIST (National Institute of Standards and Technology). A.1 SI PREFIXES You need to know the SI prefixes. They tell you the order of magnitude of the units of whatever physical quantity they are attached to. It is absolutely essential that you know them. They are widely used, and when you are wrong about them, you make mistakes of factors of thousands! Maybe you can absorb them by os- mosis as you use them; maybe you need to get them by heart by the purest of rote learning; maybe you can come up with a clever mnemonic; 633 634 APPENDIX A. USEFUL INFORMATION TABLE A.1 SI prefixes Factor Prefix Symbol Factor Prefix Symbol 1018 exa E 10−1 deci d 1015 peta P 10−2 centi c 1012 tera T 10−3 milli m 109 giga G 10−6 micro μ 106 mega M 10−9 nano n 103 kilo k 10−12 pico p 102 hecto h 10−15 femto f 101 deka da 10−18 atto a maybe (and this would be best) you can learn them attached to particular physical situations and quantities, as suggested in Chap. 2. However you do it, learn them! They are listed in Table A.1. A.2 BASIC PHYSICAL CONSTANTS You need to know some basic physical constants. These set the scale of the phenomena of the physical world. Which ones are most important depends on the physical situation under consideration. In this book, with its emphasis on atoms and their parts, the elementary charge; the masses of the electron, the proton, and the neutron; and the values of the Planck and Boltzmann constants are very important. When you deal with macroscopic quantities of atoms in the laboratory, Avogadro’s number and Earth’s gravity are important. For convenient reference Table A.2 lists the official values of these constants in SI units. Table A.3 lists the ones you need to know in the units in which you need to know them. A.3 CONSTANTS THAT YOU MUST KNOW You need to be able to calculate quickly and easily with these constants. For this purpose, you need the constants expressed as much as possible in terms of units chosen to match the natural scale of atoms. Electron volts (eV) and nanometers (nm) are convenient for atoms, while megaelectron volts (MeV) and femtometers (fm) are a good choice for nuclei. It is also often simpler to work with masses in units of eV/c2. A.3 CONSTANTS THAT YOU MUST KNOW 635 TABLE A.2 Basic physical constants Name of constant Symbol Value −27 Atomic mass unit mu or u 1.661 × 10 kg 23 −1 Avogadro constant NA 6.022 × 10 mol −11 Bohr radius a0 5.292 × 10 m −23 −1 Boltzmann constant kB 1.381 × 10 J·K 8.617 × 10−5 eV·K−1 Charge-to-mass ratio of electron e/m −1.759 × 1011 C·kg−1 9 2 −2 Coulomb constant kc or 8.988 × 10 N·m ·C 1 4π0 −31 Electron mass me 9.109 × 10 kg Elementary charge e 1.602 × 10−19 C Faraday constant F 96485 C·mol−1 Intensity of Earth’s gravitational field g 9.82 N·kg−1 (m·s−2) Molar gas constant R 8.314 J·mol−1·K−1 −27 Neutron mass mn 1.675 × 10 kg Planck constant h 6.626 × 10−34 J·s 4.136 × 10−15 eV·s h × −34 · ¯h = 2π 1.055 10 J s 6.582 × 10−16 eV·s −27 Proton mass mp 1.673 × 10 kg 7 −1 Rydberg constant R∞ 1.09737 × 10 m Speed of light c 2.99792458 × 108 m·s−1 Table A.3 gives constants, combinations of constants, and masses in terms of these more convenient units. The combinations simplify calculations of energies, wavelengths, and frequencies that are frequently made in this course. The Remark column tells you when the constant is one that you absolutely need to know. No kidding! These constants are of fundamental importance. One goal of this book is to show how the constants interrelate and how they specify the scale of observed effects and phenomena. They specify the scales and magnitudes 636 APPENDIX A. USEFUL INFORMATION TABLE A.3 Constants in convenient energy units Name Symbol Value Remark Planck constant h 4.14 × 10−15 eV·s hc 1240 eV·nm know this one! Reduced Planck h × −16 · constant: 2π ¯h 6.58 10 eV s ¯hc 197 eV·nm know as ≈ 200 eV nm ¯hc 197 MeV·fm know as ≈ 200 MeV fm 2 Coulomb force kce 1.44 eV·nm know this numerator Thermal energy at T = 300 K kBT 0.0259 eV remember as ≈ 1/40 eV h¯2 0 2 Bohr radius a = ke me 0.0529 nm ke2 Fine structure α = hc¯ 1/137.036 no units constant Rydberg energy hcR∞ 13.61 eV know this one 2 Electron mass mec 511 keV know this 2 Proton mass mpc 938.3 MeV know ≈ 938 MeV 2 Neutron mass mnc 939.6 MeV know mn is 1.29 MeV >mp 2 Atomic mass unit u 931.50 MeV/c remember 1 u ≈ mp Speed of light c 3 × 108 m·s−1 know this Elementary charge e 1.6 × 10−19 C know this of the quantities with which physicists have built a consistent and in- formative picture of the microphysical world and its connection to the macrophysical world where we live and do physics. A.4 MISCELLANEOUS Table A.4 contains some constants used occasionally in this course, including constants having to do with Earth, Moon, and Sun. Table A.5 gives conversion factors between some especially common English units and their metric equivalents. A.5 NAMES OF SOME SI DERIVED UNITS 637 TABLE A.4 Miscellaneous occasionally used constants Name Symbol Value Units Remarks 24 Earth’s mass M⊕ 6 × 10 kg 10 moles of kilograms 11 Earth–Sun distance RES 1.5 × 10 m 1 A.U. 6 Earth radius R⊕ 6.366 × 10 m2πR⊕ =40Mm 8 Earth–Moon distance REM 3.82 × 10 m60R⊕ Moon’s mass M) 0.01234 M⊕ M⊕/81 30 Sun’s mass M 2 × 10 kg 333 000 M⊕ Viscosity of air η 18.3 μPa·sat20◦C −1 ◦ Speed of sound in air vs 343 m s at 20 C TABLE A.5 Some conversion factors between english and metric units English English metric 1in 2.54cm 1 ft 12 in 30.48 cm 1 mile 5280 ft 1609.3 m 3.28 ft 1 m 0.396 in 1 cm 1 mph 1.467 ft/s 0.447 m/s 0.621 mph 0.911 ft/s 1 km/hr 2.24 mph 3.28 ft/s 1 m/s 1 lb 16 oz 453.5 g 1 oz 28.3 g 2.205 lb 1 kg A.5 NAMES OF SOME SI DERIVED UNITS Table A.6 lists some names of composite SI units. There are also a num- ber of non-SI units that are still in use because because they are deeply embedded in engineering practice or every day life (because many peo- ple are unwilling to change their habits of thought). Table A.6 lists some of these non-SI units along with their abbreviations and their SI equiva- lents. The entries in the table are in alphabetical order according to their abbreviations. 638 APPENDIX A. USEFUL INFORMATION TABLE A.6 Commonly used units and abbreviations quantity Name Abbrev. SI units current ampere A A length Angstrom A10˚ −10 m pressure atmosphere atm 101.3 kPa area barn b 10−24 m2 pressure bar bar 100 kPa energy calorie cal 4.1858 J electric charge coulomb C A·s viscosity centipoise cp 10−3 Pa·s energy electron volt eV 1.602 × 10−19 J magnetic field gauss G 10−4 T frequency hertz Hz s−1 energy joule J kg·m2·s−2 =N·m temperature kelvin K K mass kilogram kg kg volume liter L 10−3 m3 length meter m m pressure millimeters of mercury mm Hg 133.32 Pa volume cubic meter m3 m3 amount mole mol mol force newton N kg·m·s−2 electric field newton per coulomb N·C−1 N·C−1 pressure pascal Pa N·m−2 viscosity pascal seconds Pa·s angle radian rad rad time second s s magnetic field tesla T kg·s−1·C−1 pressure torr torr 133.32 Pa mass atomic mass unit u 1.6605 × 10−27 kg electric potential volt V J·C−1 electric field volts per meter V·m−1 N·C−1 power watt W J·s−1 angle degree ◦ 1.7453 × 10−2 rad A.6 SI BASE UNITS 639 TABLE A.7 SI base units Name Symbol Definition meter m The meter is the length of path traveled by light in vacuum during a time interval of 1/299 792 458 of a second.