Let There Be Light: The Story Of Light From Atoms To Galaxies (2nd Edition) The Story of Light from Atoms to Galaxies

This book is the first of its kind devoted to the key role played by light and electromagnetic radiation in the universe. Readers are introduced to philosophical hypotheses such as the economy, symmetry and the universality of natural laws, and are then guided to practical consequences such as the rules of geometrical optics and even Einstein's well-known but mysterious relationship, E = mc2. Most chapters feature a pen picture of the life and character of a relevant scientific figure. These 'Historical Interludes' include, among others, Galileo's conflicts with the Inquisition, Fourier's taunting of the guillotine, Neils Bohr and World War II, and the unique character of Richard Feynman. This second edition has been revised to present information in a more accessible style. Most of the mathematical jargon and equations from the first edition have been transformed into layman's terms. More historical materials have been included to account for the application and understanding of the phenomena of light from pre-historic to present times. The book will be of interest to students and teachers, as well as general readers interested in physics. Contents......Page 16 Preface to the First Edition......Page 8 Preface to the Second Edition......Page 10 Acknowledgements......Page 14 Chapter 1 Introducing Light......Page 22 The middle ages......Page 23 The visible spectrum......Page 25 The astronomical method......Page 26 Terrestrial measurement......Page 27 The speed of light in context......Page 29 The journey of a photon......Page 30 The eye is like a digital camera......Page 32 Two computers — the back of the eye and the brain......Page 33 Why is the grass green?......Page 34 Seeing in the dark......Page 35 Contradictory evidence......Page 36 Light as a wave......Page 37 James Clerk Maxwell......Page 38 Light as a particle......Page 39 An illustration of duality?......Page 40 Particles have wave properties......Page 41 The Copenhagen interpretation......Page 42 The universal messenger......Page 43 The quickest route......Page 44 Light takes the quickest route......Page 45 The quickest path via a reflection......Page 46 The law of reflection......Page 47 A plane mirror......Page 48 Reversal from left to right......Page 49 A spherical concave mirror......Page 50 Applications of concave mirrors......Page 53 The ‘death rays’ of Archimedes......Page 54 A historical interlude: Pierre de Fermat (1601–1665)......Page 56 Making visible things we cannot see......Page 60 The refractive index......Page 61 The lifeguard problem......Page 62 Snell’s law......Page 63 The reverse journey......Page 64 Apparent depth......Page 65 Practical applications of total internal reflection......Page 66 Light pipes and optical fibres......Page 67 Freedom of choice when a ray meets a boundary......Page 68 The mystery......Page 69 A practical puzzle — two-way mirrors......Page 70 Converging lenses......Page 71 Fermat’s principle applied to lenses......Page 72 Ray tracing through a thin lens......Page 73 Principal rays (thin lenses)......Page 74 Breaking the symmetry......Page 75 Masking a lens......Page 77 3.4 Objects and images: diverging lenses......Page 78 Lenses in contact......Page 79 The power of a lens......Page 80 Accommodation......Page 81 Hypermetropia (long-sightedness)......Page 83 Distant objects......Page 84 Nearer but not clearer......Page 86 The simple magnifier......Page 87 Compound microscopes......Page 90 Telescopes......Page 91 3.9 A final note on Fermat’s principle......Page 92 The pioneers of generalized classical mechanics......Page 93 When light reaches us after a long, long journey......Page 94 Philosophical reasons why the earth should be round......Page 95 Experimental evidence that the earth is round......Page 96 The phases of the moon......Page 97 A lunar eclipse......Page 98 A solar eclipse......Page 100 Relative sizes of the sun and the moon......Page 102 Shrinking shadows......Page 103 The distance to the sun......Page 106 A practical problem......Page 107 Astronomical distances......Page 109 Ptolemy’s geocentric model......Page 110 Frames of reference......Page 112 Copernicus and the heliocentric model......Page 113 Where did the epicycles come from?......Page 116 4.6 After Copernicus......Page 117 Looking back with hindsight: why Brahe did not see any parallax......Page 118 Kepler’s discovery......Page 119 Galileo Galilei (1564–1642)......Page 120 4.7 The solar system in perspective......Page 123 A historical interlude: Galileo Galilei (1564–1642)......Page 125 5.1 The birth of astrophysics......Page 132 Isaac Newton and gravitation......Page 133 Falling without getting nearer......Page 134 The mystery of gravitation......Page 136 Newton’s law of gravitation......Page 137 Testing the law......Page 138 Acceleration of the moon towards the earth......Page 140 Explanation of Kepler’s laws......Page 141 Predicting the existence of new planets......Page 142 Neptune is there!......Page 143 Planets of other suns......Page 144 Other galaxies......Page 147 5.4 Reconstructing the past......Page 149 The Big Bang theory......Page 150 A blast from the past......Page 151 White dwarfs......Page 153 Supernovae......Page 154 Supernovae in other galaxies......Page 155 Pulsars......Page 157 Black holes......Page 159 Escape velocities......Page 161 How to ‘see’ the invisible......Page 162 Time stands still......Page 163 A historical interlude: Isaac Newton (1642–1727)......Page 164 6.1 Waves — the basic means of communication......Page 170 Mechanical waves in a medium......Page 172 Transverse waves......Page 173 Longitudinal waves......Page 174 Generating the sine function......Page 177 An expression for a sine wave in motion......Page 178 The superposition principle......Page 179 Path difference and phase difference......Page 180 When two waves travelling in opposite directions meet......Page 181 A string fixed at both ends......Page 183 Standing waves......Page 184 6.4 Forced oscillations and resonance......Page 185 6.5 Natural frequencies of vibration and resonance......Page 186 The Tacoma Narrows Bridge disaster......Page 187 The Mexico City earthquake......Page 188 6.6 Diffraction — waves can bend around corners......Page 189 6.7 The magic of sine and the simplicity of nature......Page 190 The sum of a number of sine waves......Page 191 A historical interlude: Jean Baptiste Joseph Fourier (1768–1830)......Page 192 Sound as a pressure wave......Page 196 The speed of sound......Page 197 Ultrasound and infrasound......Page 198 Sound navigation and ranging (SONAR)......Page 199 Ultrasound in nature......Page 201 Ultrasound in medicine......Page 202 7.3 The superposition of sound waves......Page 208 Standing waves......Page 209 7.4 Sound intensity......Page 212 Real and perceived differences in the intensity of sound......Page 213 Quantifying perception......Page 214 Intensity level (loudness)......Page 216 The ‘annoyance factor’......Page 218 7.5 Other sensations......Page 219 Tone quality......Page 221 Propagation of sound in open and confined spaces......Page 222 String instruments......Page 224 Wind instruments......Page 225 A moving observer......Page 226 A moving source......Page 227 Shock waves......Page 228 Shock waves and light......Page 230 A historical interlude: The sound barrier......Page 231 Chapter 8 Light as a Wave......Page 236 The mystery of waves in nothing......Page 237 Superposition......Page 238 Huygens’ principle......Page 239 Huygens’ principle and refraction......Page 240 Diffraction......Page 242 Huygens’ principle and diffraction......Page 243 Diffraction of light......Page 244 Other apertures......Page 246 The curious case of the opaque disc......Page 247 Images may overlap......Page 248 The Rayleigh criterion......Page 249 8.5 Other electromagnetic waves......Page 250 Message from the stars......Page 251 Other windows on the universe......Page 252 Young’s experiment......Page 253 Thin film interference......Page 256 Non-reflective coatings......Page 257 8.8 Diffraction gratings......Page 259 Practical diffraction gratings......Page 261 8.9 Other ‘lights’......Page 262 X-ray diffraction......Page 263 8.10 Coherence......Page 267 The question of phase......Page 268 Polarization of electromagnetic waves......Page 269 What happens to light as it passes through a polaroid?......Page 270 Polarization by reflection......Page 272 A historical interlude: Thomas Young (1773–1829)......Page 273 Photography......Page 276 History of the photograph......Page 278 Colour photography......Page 281 Digital photography......Page 282 Interpretation of photographic images......Page 283 The inventor......Page 284 The principle......Page 285 Making a hologram......Page 286 Why does a holographic image look so real?......Page 288 Applications of holography......Page 289 The gravitational force......Page 292 The electrostatic force......Page 293 Coulomb’s law......Page 295 Vector fields......Page 296 A picture to represent a physical law......Page 297 Gauss’s theorem......Page 299 The energy in an electric field......Page 303 Magnetic materials......Page 304 Electric currents......Page 306 Oersted’s discovery......Page 307 Ampère’s law......Page 309 Summary......Page 311 The effect of a magnetic field on an electric charge......Page 312 Definition of electrical units......Page 313 Electromagnetism......Page 314 The interaction between moving charges......Page 315 Faraday’s discovery......Page 316 Faraday’s law of electromagnetic induction......Page 318 Putting facts together......Page 319 An important extension to Ampère’s law......Page 320 The four laws......Page 322 Making an electromagnetic pulse......Page 324 The speed of the magnetic tidal wave......Page 325 Cause and effect — a summary......Page 328 Putting theory into practice......Page 330 A historical interlude: James Clerk Maxwell (1831–1879)......Page 332 The light from hot soot......Page 338 How does matter emit electromagnetic energy?......Page 339 Experimental results — the blackbody radiation spectrum......Page 340 The Stefan–Boltzmann law......Page 341 Wien’s displacement law......Page 342 Cavity radiation......Page 343 Wien’s spectral distribution law......Page 345 A cavity model based on the wave nature of light......Page 347 How can the theoretical models be ‘half right’?......Page 348 The formula — but not the explanation......Page 349 Nature’s secret......Page 350 The quantum hypothesis......Page 351 Quantum discrimination......Page 352 The distribution of energy among the oscillators......Page 353 The average energy......Page 354 What does the quantum do after it is emitted?......Page 355 A new philosophy......Page 356 A historical interlude: Max Planck (1858–1947)......Page 357 Chapter 12 The Development of Quantum Mechanics......Page 362 From oscillators to photons to other things......Page 363 The quantum enters the picture......Page 364 Quantum jumps — light comes out of the atom......Page 366 The demise of determinism......Page 367 A new way of thinking......Page 368 Light from the hydrogen atom......Page 369 A matrix for everything......Page 370 The laws of nature......Page 371 Matrices do not commute!......Page 372 Laws of nature must be built into the matrices......Page 373 One measurement disturbs the other......Page 374 A ‘table top’ experiment with polaroids......Page 375 What we have learned from the experiment......Page 376 Experimenting with a series of polaroids......Page 377 The uncertainty principle......Page 379 The Schrödinger approach......Page 381 De Broglie’s original idea......Page 382 Adapting de Broglie waves......Page 384 Uncertainty from another aspect......Page 385 A wider view......Page 386 Relativity and quantum mechanics......Page 387 Triumph out of difficulty......Page 388 Positron emission tomography......Page 389 Antiprotons and antihydrogen......Page 391 Critics of the Copenhagen interpretation......Page 392 Bell’s theorem......Page 393 A precursor of quantum reality......Page 394 A historical interlude: Niels Bohr (1885–1962)......Page 395 Chapter 13 Atoms of Light Acting as Particles......Page 402 Short sharp shocks......Page 403 There are ‘grains’ in the light beam......Page 404 How long would we expect to wait? An order-of-magnitude calculation......Page 405 The ‘lucky’ electron......Page 406 Einstein’s photoelectric equation......Page 407 Millikan’s experiment......Page 409 Current flowing uphill......Page 410 Practical applications......Page 412 Energy transfer......Page 415 Collision of X-ray photons......Page 416 The photon loses energy but does not slow down......Page 417 A historical interlude: Robert A. Millikan (1868–1953)......Page 419 Chapter 14 Atoms of Light Behaving as Waves......Page 426 Detecting a single photon......Page 427 The long thin line......Page 428 Single slit diffraction......Page 429 Measuring ‘clicks’ as photons arrive one by one......Page 430 Separating the possible paths......Page 433 Partial reflection......Page 435 The strange theory of the photon......Page 438 The rotating amplitude vector......Page 439 Why light appears to travel in straight lines......Page 441 How can we believe all this?......Page 442 What then is new?......Page 443 Quantum electrodynamics......Page 444 A historical interlude: Richard Feynman (1918–1988)......Page 446 Empty space is the same everywhere and for everyone......Page 452 Space and the ancient philosophers......Page 453 Space and time — according to Isaac Newton......Page 455 Starting with a clean slate......Page 456 Frames of reference — defining a point of view......Page 457 Specifying the prejudices......Page 459 The Michelson–Morley experiment......Page 461 Timing the ferry......Page 462 Details of the experiment......Page 464 The new model......Page 466 Nature does not discriminate......Page 467 Galileo had the right idea!......Page 469 The Galilean transformation......Page 470 Galileo’s first step......Page 471 Einstein’s second postulate......Page 472 A paradox* — how can they possibly get the same result?......Page 473 Einstein puts the facts together......Page 474 The impossible’ in mathematical form......Page 475 The gamma factor......Page 476 15.6 Pythagoras re-visited......Page 478 Moving on to three dimensions......Page 479 15.7 The fourth dimension......Page 480 Invariant interval in space–time......Page 481 The smoking astronaut......Page 483 What is the meaning of ‘simultaneous’?......Page 485 A historical interlude: Hendrik A. Lorentz (1853–1928)......Page 486 Chapter 16 Relativity Part 2: Verifiable Predictions......Page 492 Time dilation in action......Page 493 Living on borrowed time?......Page 494 16.2 Bringing energy into the picture......Page 495 Conservation of momentum — a thought experiment with snooker balls......Page 496 Interacting with another time frame......Page 497 Relativistic definition of momentum......Page 499 Energy content’......Page 500 Putting things into perspective......Page 504 High-energy particle accelerators......Page 505 Nuclear structure......Page 507 Nuclear fission......Page 509 A synopsis......Page 510 A historical interlude: Albert Einstein (1879–1955)......Page 511 Then there was light......Page 516 Collisions make particles......Page 517 Prediction and discovery of the π meson......Page 518 The forces between the particles......Page 520 The laws of the world of elementary particles......Page 522 Quarks......Page 524 The return of photographic emulsion......Page 528 More quarks......Page 531 The role of light as the carrier of the electromagnetic force......Page 532 Unification — the long hard road......Page 533 The heavy photon......Page 534 The Higgs boson......Page 537 The full circle......Page 539 Index......Page 540 About the Authors......Page 552 This book is the first of its kind devoted to the key role played by light and electromagnetic radiation in the universe. Readers are introduced to philosophical hypotheses such as the economy, symmetry and the universality of natural laws, and are then guided to practical consequences such as the rules of geometrical optics and even Einstein's well-known but mysterious relationship, E = mc2. Most chapters feature a pen picture of the life and character of a relevant scientific figure. These 'Historical Interludes' include, among others, Galileo's conflicts with the Inquisition, Fourier's taunting of the guillotine, Neils Bohr and World War II, and the unique character of Richard Feynman. The second edition has been revised and made more accessible to the general reader. Whenever possible, the mathematical material of the first edition has been replaced by appropriate text to give a verbal account of the mystery of the phenomenon of light and how its understanding has developed from pre-historic to present times. The emphasis is on reading for interest and enjoyment; formulae or equations which underpin and reinforce the argument are presented in a form which does not interfere with the flow of the text. The book will be of interest to students and teachers, as well as general readers interested in physics. Publisher This book is the first of its kind to devote itself at this level to the key role played by light and electromagnetic radiation in the universe. Readers are introduced to philosophical hypotheses such as the economy, symmetry, and universality of natural laws, and are then guided to practical consequences such as the rules of geometrical optics and even Einstein's well-known but mysterious relationship, E = mc[superscript 2]. Most chapters feature a pen picture of the life and character of a relevant scientific figure. These Historical Interludes include, among others, Galileo's conflicts with the Inquisition, Fourier's taunting of the guillotine, Neils Bohr and World War II, and the unique character of Richard Feynman.