818 



SMITHSONIAN PHYSICAL TABLES 



Radio radiation — continued 

 reflection, 444 



atmosphere layers, 444 

 transmission, 444 

 factors, 444 



over ground, 444 

 bad, 444 

 good, 444 

 over sea water, 444 

 Radium: 



danger ranges for persons working with 

 Ra, 686, 689, 690 

 amounts of radium, 690 

 emanation, vapor pressure (cmHg), 682 

 energy emitted by 1 g Ra in equilibrium 



691 

 protection for 8 hours p?r day exposure, 

 686 

 distance, 686 

 thickness of lead, 690 

 safe working distance, 689 

 Radius: atomic, 643, 644 

 gyration, 27 

 ionic, 648 

 molecules, 645 

 Range of particles, 654 

 Rankin temperature scale, 9 

 Rayon, 243 



Reaumur temperature scale, 9 

 Receivers for radiation, 548 



blackening, 548 

 Reflection factor: angle, 549, 550 

 building materials, 553 

 diffuse, 551, 555 

 formula, 549 

 long wavelengths, 554, 555 



materials for, 554, 555, 556 

 metals, 550, 552 



ultraviolet, 550 

 pigments, dry, 551 

 powders, 550, 551 

 sand, 554 

 snow, 554 



surfaces, with angle, 550 

 tungsten, 555 

 Refraction, index of (see also Index of Re- 

 fraction), 509, 532 

 Refractive indices with microscope, 561 



materials for, 561 

 Reluctance, 18 

 Resilience, 6 

 Resistance (electric), 11 



alternating to direct current, 419 



diameter wire for ratio 1.01, 420 

 average pressure coefficients for metals, 



389 

 bismuth, temperature variation, 

 transverse magnetic field, 463 

 change of: metals, transverse magnetic 

 field, 463 

 nickel, 463 

 high-frequency, conductors, 417-419 

 calculation of, 417, 418 

 resistance ratio, 418 

 temperature, 393 

 human body, 375 



Resistance — continued 



increase of, due to transverse magnetic 



field, nickel, 463 

 manganin, under pressure, 389 

 mercury, under pressure, 389 

 metals, effect of tension, 387 



pressure, 388 

 nickel, magnetic field, 463 

 of conductor, 11 

 pressure coefficient, 388, 389 

 proximity factor, 419 

 ratio, wire diameters, ac to dc resistances, 



419 

 skin effect, 417 

 standard, 16, 19 



annealed copper, 404 

 temperature 



high, 393 



low, 393 

 tension, 387 

 tubular conductors, 418 



frequency, 418 

 variation with pressure (metals), 388 

 Resistivity (see also Conductivity), 12, 13, 



19 

 alloys, 384, 390 

 aluminium, 404 



at high and low temperatures, 393 

 copper, 404 



temperature coefficient, 406 

 dielectrics (solid), surface, 395 



volume, 395 

 elements, 384, 387 

 glass vs. temperature, 396 

 mercury vs. pressure, 389 

 metals, 384 



vs. pressure, 388 



vs. temperature, 385 

 minerals, miscellaneous, 395 

 oxides, 395 

 plastics, 239 

 pressure effect, 388 

 rocks, 395 

 sea water, 396 

 soils, 395 



solutions (electrolytic), 397 

 surface, solid dielectric, 395 

 temperature: coefficient, 384 



low, 393 

 thermal, 44 



volume, of solid dielectrics, 395 

 water, natural, 396 



sea (high-frequency), 396 

 Resolving power (photography), 564 

 Rest mass, 654 



Restrahlung bands, various materials, 555 

 Reverberation time, 315 

 optimum, 316 

 room type, 317 

 Reynolds number, 337 

 Rigidity modulus, number of materials, 226 



and temperature, 227 

 Ring (magnetic) specimens, corrections for, 



464 

 Rock salt: index of refraction, 518 

 transmission, 517 



