domingo, 15 de septiembre de 2013

The Feynman Lectures on Physics, Volume I

The Feynman Lectures on Physics

Feynman • Leighton • Sands

Caltech and The Feynman Lectures Website are pleased to present this online edition of The Feynman Lectures on Physics. Now, anyone with internet access and a web browser can enjoy reading a high-quality up-to-date copy of Feynman's legendary lectures. This edition has been designed for ease of reading on devices of any size or shape; text, figures and equations can all be zoomed without degradation.1
served by Caltech (generally faster)

served by The Feynman Lectures Website
mainly mechanics, radiation and heat

mainly mechanics, radiation and heat
For comments or questions about this edition please contact Michael Gottlieb.
Richard Feynman, Robert Leighton and Matthew Sands, talking with a teaching assistant after the lecture on The Dependence of Amplitudes on Time,  April 29, 1963.
Photograph by Tom Harvey. Copyright © California Institute of Technology.

Contributions from many parties have enabled and benefitted the creation of the HTML edition of The Feynman Lectures on Physics. We wish to thank
  • Carver Mead, for his warm encouragement and generous financial support, without which this edition would have been impossible,
  • Thomas Kelleher and Basic Books, for their open-mindedness in allowing this edition to be published free of charge,
  • Adam Cochran, for tying up the many slippery loose ends that needed to come together in order for this edition to be realized,
  • Alan Rice for his steadfast enthusiasm for this project, and for rallying the support of Caltech's Division of Physics Math and Astronomy ,
  • Michael Hartl and Evan Dorn, for the excellent job they did converting Volume I of the FLP LaTeX manuscript into HTML.

  1. This HTML5-based edition features LaTeX equations rendered by MathJax JavaScript, and scalable vector graphic (SVG) figures. Your browser must support javascript and permit scripts from We recommend using a modern browser; some older browsers may not display this edition correctly. PNG figures (that degrade when scaled) may be served to browsers that do not support SVG. We do not support versions of Internet Explorer older than 8.0. For information about MathJax features and accessibility options, please visit the MathJax User Help page. (This is a work in progress. Initially we are publishing Volume I; We hope to eventually publish Volumes II and III, and lectures will be posted as time and funds permit.)

The Feynman Lectures on Physics, Volume I

Preface to the New Millennium Edition

Feynman's Preface
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These are the lectures in physics that I gave last year and the year before to the freshman and sophomore classes at Caltech. The lectures are, of course, not verbatim---they have been edited, sometimes extensively and sometimes less so. The lectures form only part of the complete course. The whole group of 180 students gathered in a big lecture room twice a week to hear these lectures and then they broke up into small groups of 15 to 20 students in recitation sections under the guidance of a teaching assistant. In addition, there was a laboratory session once a week.

The special problem we tried to get at with these lectures was to maintain the interest of the very enthusiastic and rather smart students coming out of the high schools and into Caltech. They have heard a lot about how interesting and exciting physics is---the theory of relativity, quantum mechanics, and other modern ideas. By the end of two years of our previous course, many would be very discouraged because there were really very few grand, new, modern ideas presented to them. They were made to study inclined planes, electrostatics, and so forth, and after two years it was quite stultifying. The problem was whether or not we could make a course which would save the more advanced and excited student by maintaining his enthusiasm.

The lectures here are not in any way meant to be a survey course, but are very serious. I thought to address them to the most intelligent in the class and to make sure, if possible, that even the most intelligent student was unable to completely encompass everything that was in the lectures---by putting in suggestions of applications of the ideas and concepts in various directions outside the main line of attack. For this reason, though, I tried very hard to make all the statements as accurate as possible, to point out in every case where the equations and ideas fitted into the body of physics, and how---when they learned more---things would be modified. I also felt that for such students it is important to indicate what it is that they should---if they are sufficiently clever---be able to understand by deduction from what has been said before, and what is being put in as something new. When new ideas came in, I would try either to deduce them if they were deducible, or to explain that it was a new idea which hadn't any basis in terms of things they had already learned and which was not supposed to be provable---but was just added in.

At the start of these lectures, I assumed that the students knew something when they came out of high school---such things as geometrical optics, simple chemistry ideas, and so on. I also didn't see that there was any reason to make the lectures in a definite order, in the sense that I would not be allowed to mention something until I was ready to discuss it in detail. There was a great deal of mention of things to come, without complete discussions. These more complete discussions would come later when the preparation became more advanced. Examples are the discussions of inductance, and of energy levels, which are a first brought in in a very qualitative way and are later developed more completely.

At the same time that I was aiming at the more active student, I also wanted to take care of the fellow for whom the extra fireworks and side applications are merely disquieting and who cannot be expected to learn most of the material in the lecture at all. For such students I wanted there to be at least a central core or backbone of material which he could get. Even if he didn't understand everything in a lecture, I hoped he wouldn't get nervous. I didn't expect him to understand everything, but only the central and most direct features. It takes, of course, a certain intelligence on his part to see which are the central theorems and central ideas, and which are the more advanced side issues and applications which he may understand only in later years.

In giving these lectures there was one serious difficulty: in the way the course was given, there wasn't any feedback from the students to the lecturer to indicate how well the lectures were going over. This is indeed a very serious difficulty, and I don't know how good the lectures really are. The whole thing was essentially an experiment. And if I did it again I wouldn't do it the same way---I hope I don't have to do it again! I think, though, that things worked out---so far as the physics is concerned---quite satisfactorily in the first year.

In the second year I was not so satisfied. In the first part of the course, dealing with electricity and magnetism, I couldn't think of any really unique or different way of doing it---of any way that would be particularly more exciting than the usual way of presenting it. So I don't think I did very much in the lectures on electricity and magnetism. At the end of the second year I had originally intended to go on, after the electricity and magnetism, by giving some more lectures on the properties of materials, but mainly to take up things like fundamental modes, solutions of the diffusion equation, vibrating systems, orthogonal functions, … developing the first stages of what are usually called "the mathematical methods of physics.'' In retrospect, I think that if I were doing it again I would go back to that original idea. But since it was not planned that I would be giving these lectures again, it was suggested that it might be a good idea to try to give an introduction to the quantum mechanics---what you will find in Volume III.

It is perfectly clear that students who will major in physics can wait until their third year for quantum mechanics. On the other hand, the argument was made that many of the students in our course study physics as a background for their primary interest in other fields. And the usual way of dealing with quantum mechanics makes that subject almost unavailable for the great majority of students because they have to take so long to learn it. Yet, in its real applications---especially in its more complex applications, such as in electrical engineering and chemistry---the full machinery of the differential equation approach is not actually used. So I tried to describe the principles of quantum mechanics in a way which wouldn't require that one first know the mathematics of partial differential equations. Even for a physicist I think that is an interesting thing to try to do---to present quantum mechanics in this reverse fashion---for several reasons which may be apparent in the lectures themselves. However, I think that the experiment in the quantum mechanics part was not completely successful---in large part because I really did not have enough time at the end (I should, for instance, have had three or four more lectures in order to deal more completely with such matters as energy bands and the spatial dependence of amplitudes). Also, I had never presented the subject this way before, so the lack of feedback was particularly serious. I now believe the quantum mechanics should be given at a later time. Maybe I'll have a chance to do it again someday. Then I'll do it right.

The reason there are no lectures on how to solve problems is because there were recitation sections. Although I did put in three lectures in the first year on how to solve problems, they are not included here. Also there was a lecture on inertial guidance which certainly belongs after the lecture on rotating systems, but which was, unfortunately, omitted. The fifth and sixth lectures are actually due to Matthew Sands, as I was out of town. The question, of course, is how well this experiment has succeeded. My own point of view---which, however, does not seem to be shared by most of the people who worked with the students---is pessimistic. I don't think I did very well by the students. When I look at the way the majority of the students handled the problems on the examinations, I think that the system is a failure. Of course, my friends point out to me that there were one or two dozen students who---very surprisingly---understood almost everything in all of the lectures, and who were quite active in working with the material and worrying about the many points in an excited and interested way. These people have now, I believe, a first-rate background in physics---and they are, after all, the ones I was trying to get at. But then, "The power of instruction is seldom of much efficacy except in those happy dispositions where it is almost superfluous.'' (Gibbon)

Still, I didn't want to leave any student completely behind, as perhaps I did. I think one way we could help the students more would be by putting more hard work into developing a set of problems which would elucidate some of the ideas in the lectures. Problems give a good opportunity to fill out the material of the lectures and make more realistic, more complete, and more settled in the mind the ideas that have been exposed.

I think, however, that there isn't any solution to this problem of education other than to realize that the best teaching can be done only when there is a direct individual relationship between a student and a good teacher---a situation in which the student discusses the ideas, thinks about the things, and talks about the things. It's impossible to learn very much by simply sitting in a lecture, or even by simply doing problems that are assigned. But in our modern times we have so many students to teach that we have to try to find some substitute for the ideal. Perhaps my lectures can make some contribution. Perhaps in some small place where there are individual teachers and students, they may get some inspiration or some ideas from the lectures. Perhaps they will have fun thinking them through---or going on to develop some of the ideas further.

Richard P. Feynman

June, 1963

Copyright © 1963, 2006, 2013 by the California Institute of Technology,
Michael A. Gottlieb, and Rudolf Pfeiffer


Chapter 1. Atoms in Motion
1-1 Introduction
1-2 Matter is made of atoms
1-3 Atomic processes
1-4 Chemical reactions

Chapter 2. Basic Physics
2-1 Introduction
2-2 Physics before 1920
2-3 Quantum physics
2-4 Nuclei and particles

Chapter 3. The Relation of Physics to Other Sciences
3-1 Introduction
3-2 Chemistry
3-3 Biology
3-4 Astronomy
3-5 Geology
3-6 Psychology
3-7 How did it get that way?

Chapter 4. Conservation of Energy
4-1 What is energy?
4-2 Gravitational potential energy
4-3 Kinetic energy
4-4 Other forms of energy

Chapter 5. Time and Distance
5-1 Motion
5-2 Time
5-3 Short times
5-4 Long times
5-5 Units and standards of time
5-6 Large distances
5-7 Short distances

Chapter 6. Probability
6-1 Chance and likelihood
6-2 Fluctuations
6-3 The random walk
6-4 A probability distribution
6-5 The uncertainty principle

Chapter 7. The Theory of Gravitation
7-1 Planetary motions
7-2 Kepler’s laws
7-3 Development of dynamics
7-4 Newton’s law of gravitation
7-5 Universal gravitation
7-6 Cavendish’s experiment
7-7 What is gravity?
7-8 Gravity and relativity

Chapter 8. Motion
8-1 Description of motion
8-2 Speed
8-3 Speed as a derivative
8-4 Distance as an integral
8-5 Acceleration

Chapter 9. Newton’s Laws of Dynamics
9-1 Momentum and force
9-2 Speed and velocity
9-3 Components of velocity, acceleration, and force
9-4 What is the force?
9-5 Meaning of the dynamical equations
9-6 Numerical solution of the equations
9-7 Planetary motions

Chapter 10. Conservation of Momentum
10-1 Newton’s Third Law
10-2 Conservation of momentum
10-3 Momentum is conserved!
10-4 Momentum and energy
10-5 Relativistic momentum

Chapter 11. Vectors
11-1 Symmetry in physics
11-2 Translations
11-3 Rotations
11-4 Vectors
11-5 Vector algebra
11-6 Newton’s laws in vector notation
11-7 Scalar product of vectors

Chapter 12. Characteristics of Force
12-1 What is a force?
12-2 Friction
12-3 Molecular forces
12-4 Fundamental forces. Fields
12-5 Pseudo forces
12-6 Nuclear forces

Chapter 13. Work and Potential Energy (A)
13-1 Energy of a falling body
13-2 Work done by gravity
13-3 Summation of energy
13-4 Gravitational field of large objects

Chapter 14. Work and Potential Energy (conclusion)
14-1 Work
14-2 Constrained motion
14-3 Conservative forces
14-4 Nonconservative forces
14-5 Potentials and fields

Chapter 15. The Special Theory of Relativity
15-1 The principle of relativity
15-2 The Lorentz transformation
15-3 The Michelson-Morley experiment
15-4 Transformation of time
15-5 The Lorentz contraction
15-6 Simultaneity
15-7 Four-vectors
15-8 Relativistic dynamics
15-9 Equivalence of mass and energy

Chapter 16. Relativistic Energy and Momentum
16-1 Relativity and the philosophers
16-2 The twin paradox
16-3 Transformation of velocities
16-4 Relativistic mass
16-5 Relativistic energy

Chapter 17. Space-Time
17-1 The geometry of space-time
17-2 Space-time intervals
17-3 Past, present, and future
17-4 More about four-vectors
17-5 Four-vector algebra

Chapter 18. Rotation in Two Dimensions
18-1 The center of mass
18-2 Rotation of a rigid body
18-3 Angular momentum
18-4 Conservation of angular momentum

Chapter 19. Center of Mass; Moment of Inertia
19-1 Properties of the center of mass
19-2 Locating the center of mass
19-3 Finding the moment of inertia
19-4 Rotational kinetic energy

Chapter 20. Rotation in space
20-1 Torques in three dimensions
20-2 The rotation equations using cross products
20-3 The gyroscope
20-4 Angular momentum of a solid body

Chapter 21. The Harmonic Oscillator
21-1 Linear differential equations
21-2 The harmonic oscillator
21-3 Harmonic motion and circular motion
21-4 Initial conditions
21-5 Forced oscillations

Chapter 22. Algebra
22-1 Addition and multiplication
22-2 The inverse operations
22-3 Abstraction and generalization
22-4 Approximating irrational numbers
22-5 Complex numbers
22-6 Imaginary exponents

Chapter 23. Resonance
23-1 Complex numbers and harmonic motion
23-2 The forced oscillator with damping
23-3 Electrical resonance
23-4 Resonance in nature

Chapter 24. Transients
24-1 The energy of an oscillator
24-2 Damped oscillations
24-3 Electrical transients

Chapter 25. Linear Systems and Review
25-1 Linear differential equations
25-2 Superposition of solutions
25-3 Oscillations in linear systems
25-4 Analogs in physics
25-5 Series and parallel impedances

Chapter 26. Optics: The Principle of Least Time
26-1 Light
26-2 Reflection and refraction
26-3 Fermat’s principle of least time
26-4 Applications of Fermat’s principle
26-5 A more precise statement of Fermat’s principle
26-6 How it works

Chapter 27. Geometrical Optics
27-1 Introduction
27-2 The focal length of a spherical surface
27-3 The focal length of a lens
27-4 Magnification
27-5 Compound lenses
27-6 Aberrations
27-7 Resolving power

Chapter 28. Electromagnetic Radiation
28-1 Electromagnetism
28-2 Radiation
28-3 The dipole radiator
28-4 Interference

Chapter 29. Interference
29-1 Electromagnetic waves
29-2 Energy of radiation
29-3 Sinusoidal waves
29-4 Two dipole radiators
29-5 The mathematics of interference

Chapter 30. Diffraction
30-1 The resultant amplitude due to n equal oscillators
30-2 The diffraction grating
30-3 Resolving power of a grating
30-4 The parabolic antenna
30-5 Colored films; crystals
30-6 Diffraction by opaque screens
30-7 The field of a plane of oscillating charges

Chapter 31. The Origin of the Refractive Index
31-1 The index of refraction
31-2 The field due to the material
31-3 Dispersion
31-4 Absorption
31-5 The energy carried by an electric wave
31-6 Diffraction of light by a screen

Chapter 32. Radiation Damping. Light Scattering
32-1 Radiation resistance
32-2 The rate of radiation of energy
32-3 Radiation damping
32-4 Independent sources
32-5 Scattering of light

Chapter 33. Polarization
33-1 The electric vector of light
33-2 Polarization of scattered light
33-3 Birefringence
33-4 Polarizers
33-5 Optical activity
33-6 The intensity of reflected light
33-7 Anomalous refraction

Chapter 34. Relativistic Effects in Radiation
34-1 Moving sources
34-2 Finding the “apparent” motion
34-3 Synchrotron radiation
34-4 Cosmic synchrotron radiation
34-5 Bremsstrahlung
34-6 The Doppler effect
34-7 The ?, k four-vector
34-8 Aberration
34-9 The momentum of light

Chapter 35. Color Vision
35-1 The human eye
35-2 Color depends on intensity
35-3 Measuring the color sensation
35-4 The chromaticity diagram
35-5 The mechanism of color vision
35-6 Physiochemistry of color vision

Chapter 36. Mechanisms of Seeing
36-1 The sensation of color
36-2 The physiology of the eye
36-3 The rod cells
36-4 The compound (insect) eye
36-5 Other eyes
36-6 Neurology of vision

Chapter 37. Quantum Behavior
37-1 Atomic mechanics
37-2 An experiment with bullets
37-3 An experiment with waves
37-4 An experiment with electrons
37-5 The interference of electron waves
37-6 Watching the electrons
37-7 First principles of quantum mechanics
37-8 The uncertainty principle

Chapter 38. The Relation of Wave and Particle Viewpoints
38-1 Probability wave amplitudes
38-2 Measurement of position and momentum
38-3 Crystal diffraction
38-4 The size of an atom
38-5 Energy levels
38-6 Philosophical implications

Chapter 39. The Kinetic Theory of Gases
39-1 Properties of matter
39-2 The pressure of a gas
39-3 Compressibility of radiation
39-4 Temperature and kinetic energy
39-5 The ideal gas law

Chapter 40. The Principles of Statistical Mechanics
40-1 The exponential atmosphere
40-2 The Boltzmann law
40-3 Evaporation of a liquid
40-4 The distribution of molecular speeds
40-5 The specific heats of gases
40-6 The failure of classical physics

Chapter 41. The Brownian Movement
41-1 Equipartition of energy
41-2 Thermal equilibrium of radiation
41-3 Equipartition and the quantum oscillator
41-4 The random walk

Chapter 42. Applications of Kinetic Theory
42-1 Evaporation
42-2 Thermionic emission
42-3 Thermal ionization
42-4 Chemical kinetics
42-5 Einstein’s laws of radiation

Chapter 43. Diffusion
43-1 Collisions between molecules
43-2 The mean free path
43-3 The drift speed
43-4 Ionic conductivity
43-5 Molecular diffusion
43-6 Thermal conductivity

Chapter 44. The Laws of Thermodynamics
44-1 Heat engines; the first law
44-2 The second law
44-3 Reversible engines
44-4 The efficiency of an ideal engine
44-5 The thermodynamic temperature
44-6 Entropy

Chapter 45. Illustrations of Thermodynamics
45-1 Internal energy
45-2 Applications
45-3 The Clausius-Clapeyron equation

Chapter 46. Ratchet and pawl
46-1 How a ratchet works
46-2 The ratchet as an engine
46-3 Reversibility in mechanics
46-4 Irreversibility
46-5 Order and entropy

Chapter 47. Sound. The wave equation
47-1 Waves
47-2 The propagation of sound
47-3 The wave equation
47-4 Solutions of the wave equation
47-5 The speed of sound

Chapter 48. Beats
48-1 Adding two waves
48-2 Beat notes and modulation
48-3 Side bands
48-4 Localized wave trains
48-5 Probability amplitudes for particles
48-6 Waves in three dimensions
48-7 Normal modes

Chapter 49. Modes
49-1 The reflection of waves
49-2 Confined waves, with natural frequencies
49-3 Modes in two dimensions
49-4 Coupled pendulums
49-5 Linear systems

Chapter 50. Harmonics
50-1 Musical tones
50-2 The Fourier series
50-3 Quality and consonance
50-4 The Fourier coefficients
50-5 The energy theorem
50-6 Nonlinear responses

Chapter 51. Waves
51-1 Bow waves
51-2 Shock waves
51-3 Waves in solids
51-4 Surface waves

Chapter 52. Symmetry in Physical Laws
52-1 Symmetry operations
52-2 Symmetry in space and time
52-3 Symmetry and conservation laws
52-4 Mirror reflections
52-5 Polar and axial vectors
52-6 Which hand is right?
52-7 Parity is not conserved!
52-8 Antimatter
52-9 Broken symmetries

Copyright © 1963, 2006, 2013 by the California Institute of Technology,
Michael A. Gottlieb, and Rudolf Pfeiffer

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