University Physics Volume 3 PDF Download – OpenStax (Optics & Modern Physics) BS Physics

BS Physics students taking a course in optics and modern physics can get “University Physics Volume 3” free from OpenStax. It is a calculus-based textbook by Samuel J. Ling, Jeff Sanny, William Moebs, and contributing authors, with 11 chapters in two units: Optics (Chapters 1–4) and Modern Physics (Chapters 5–11). Each section works through examples before a set of practice problems, and each chapter closes with Key Terms, Key Equations, and a Summary.

This is the third and final volume of OpenStax’s University Physics series. Volume 1 covers mechanics, sound, oscillations, and waves, and Volume 2 covers thermodynamics, electricity, and magnetism. Volume 3 starts with the nature of light, lenses, interference, and diffraction, then moves through special relativity, photons and matter waves, quantum mechanics, atomic structure, condensed matter, nuclear physics, and particle physics with cosmology. That makes it a strong match for a Modern Physics course.

Book Overview

Chapter List

Chapter 1: The Nature of Light

Unit 1: Optics · Difficulty: Easy · Key topics: speed of light, index of refraction, law of reflection, Snell’s law, total internal reflection, dispersion, Huygens’s principle, polarization

The book opens with light itself. It fixes the speed of light at about 3.00 × 10⁸ m/s in vacuum, defines the index of refraction as the ratio of that speed to the speed in a material, and adopts the ray model, in which light travels in straight lines. From there it works through reflection from smooth and rough surfaces, refraction and Snell’s law, and total internal reflection with its uses in fiber optics and diamonds. Dispersion explains rainbows. The chapter ends by switching to the wave picture: Huygens’s principle re-derives reflection and refraction, and polarization introduces Malus’s law and Brewster’s angle.

Key Points:

• Speed of light in vacuum: c = 2.99792458 × 10⁸ m/s; index of refraction n = c/v, so n is never below 1
• Law of reflection: the angle of reflection equals the angle of incidence (θ_r = θ_i)
• Snell’s law: n₁ sin θ₁ = n₂ sin θ₂
• Total internal reflection needs light going from a higher to a lower index and an incident angle above the critical angle, θ_c = sin⁻¹(n₂/n₁)
• Huygens’s principle: every point on a wave front is a source of wavelets, and the new wave front is tangent to all of them
• Malus’s law, I = I₀ cos²θ, gives the intensity through a polarizer; Brewster’s law, tan θ_b = n₂/n₁, gives the angle at which reflected light is completely polarized

Memory Tip: Light bends toward the normal when it enters a slower (higher-index) medium. Picture a toy car rolling onto thick carpet at an angle: the wheel that hits the carpet first slows down, and the car swings toward the perpendicular.

Common Mistake: Measuring angles from the surface instead of from the normal. Every angle in the laws of reflection and refraction is measured from the line perpendicular to the surface.

Important Questions:

• What is the critical angle for light going from water (n = 1.33) into air? sin θ_c = 1/1.33 ≈ 0.75, so θ_c ≈ 49°. Beyond this angle all the light is reflected back into the water.
• Light of intensity I₀ reaches a polarizer whose axis makes 60° with its polarization direction. What intensity passes? By Malus’s law, I = I₀ cos²60° = I₀/4.

Chapter 2: Geometric Optics and Image Formation

Unit 1: Optics · Difficulty: Medium · Key topics: plane and spherical mirrors, mirror equation, refraction at an interface, thin lenses, lens maker’s equation, the eye, camera, magnifier, microscope, telescope

This chapter is the ray-tracing toolkit. Plane mirrors form virtual, upright, same-size images. Spherical mirrors add the focal length f = R/2 and the mirror equation, plus spherical aberration. The book then treats a single refracting interface (apparent depth and the spherical-interface equation), thin lenses with converging and diverging cases, and the lens maker’s equation. These tools are applied to the eye (accommodation, myopia and hyperopia and their corrective lenses), the camera, and the simple magnifier. Microscopes and telescopes close the chapter, where the image from one element becomes the object for the next.

Key Points:

• A plane mirror always forms a virtual, upright image the same size as the object and as far behind the mirror as the object is in front
• Spherical mirror focal length: f = R/2; mirror and thin-lens equation: 1/d_o + 1/d_i = 1/f
• Magnification m = h_i/h_o = −d_i/d_o; a negative m means an inverted image
• A converging lens forms real or virtual images depending on the object position; a diverging lens forms only virtual images
• Lens maker’s equation: 1/f = (n₂/n₁ − 1)(1/R₁ − 1/R₂); optical power P = 1/f
• In multi-element systems the overall magnification is the product of the individual ones; for a telescope, M = −f_obj/f_eye

Memory Tip: For the sign convention, remember “real is positive.” A real object, a real image and the focal length of a concave (converging) mirror all take a plus sign.

Common Mistake: Treating a negative image distance as an error. A negative d_i is a valid answer and simply means the image is virtual.

Important Questions:

• A concave mirror has radius of curvature 40 cm and an object sits 30 cm in front of it. Where is the image? f = R/2 = 20 cm, so 1/d_i = 1/20 − 1/30 = 1/60 and d_i = 60 cm. The image is real, and m = −2 means it is inverted and twice the size of the object.
• Why is a nearsighted eye corrected with a diverging lens? Myopia means the eye’s optical power is too strong for distant objects. A diverging lens reduces that power, so the corrected image falls between the person’s near and far points and can be seen clearly.

Chapter 3: Interference

Unit 1: Optics · Difficulty: Medium · Key topics: Young’s double slit, path difference, constructive and destructive interference, multiple slits, thin films, phase change on reflection, Michelson interferometer

Interference is presented as the surest sign that light is a wave. The chapter starts with Young’s double-slit experiment as definitive evidence, then turns it into mathematics: the path difference from two slits is d sin θ, bright fringes occur at whole-number multiples of the wavelength and dark fringes at half-integer multiples, and the m-th bright fringe sits at y_m = mλD/d. Adding more slits (N > 2) sharpens the principal maxima. Thin films combine path difference with a 180° phase change on reflection from a higher-index medium, which explains soap-bubble colors. The Michelson interferometer closes the chapter.

Key Points:

• Double-slit maxima: d sin θ = mλ (m = 0, ±1, ±2, …); minima: d sin θ = (m + ½)λ
• On a screen a distance D away, the m-th bright fringe is at y_m = mλD/d
• With N > 2 slits, the principal maxima get more intense and narrower, and weaker secondary maxima appear between them
• Reflection from a medium of higher refractive index shifts the phase by 180° (a λ/2 shift); reflection from a lower-index medium does not
• Thin-film interference comes from light reflected off the top and bottom surfaces of the film, so path length and phase change both matter
• In a Michelson interferometer, moving one mirror by λ/2 shifts the pattern by exactly one fringe

Memory Tip: For thin films, count the phase flips before touching any formula. If exactly one of the two reflections flips the phase, the bright and dark conditions swap compared with the case of zero or two flips.

Common Mistake: Using d sin θ = mλ for dark fringes. Whole numbers of wavelengths give bright fringes; dark fringes need the half-integer form (m + ½)λ.

Important Questions:

• Two slits 0.10 mm apart are lit with 600 nm light and the screen is 1.0 m away. What is the spacing between bright fringes? Δy = λD/d = (600 × 10⁻⁹ m)(1.0 m)/(1.0 × 10⁻⁴ m) = 6.0 mm.
• Why does a thin soap film show colors? Light reflecting from the front and back surfaces of the film interferes. For a given film thickness some wavelengths reinforce and others cancel, so the film appears colored without any pigment.

Chapter 4: Diffraction

Unit 1: Optics · Difficulty: Medium · Key topics: single-slit diffraction, intensity pattern, double-slit with diffraction, diffraction gratings, Rayleigh criterion, X-ray diffraction, holography

The chapter answers a puzzle left by the interference chapter: how can one slit produce a fringe pattern? A single slit gives a broad central maximum with dimmer maxima to the sides, and the intensity is worked out with phasors as I = I₀(sin β/β)². A real double slit combines both effects, with interference fringes living inside a diffraction envelope and sometimes missing orders. Gratings extend this to many slits for sharper maxima. The chapter then shows how diffraction limits resolution through the Rayleigh criterion, how X-rays diffract from crystals, and how lasers make holography possible.

Key Points:

• Single-slit minima occur at a sin θ = mλ for m = ±1, ±2, … (there is no m = 0 minimum; the center is the brightest point)
• Single-slit intensity: I = I₀(sin β/β)², with β = πa sin θ/λ
• A missing order occurs where an interference maximum lands on a diffraction minimum
• Diffraction grating maxima follow d sin θ = mλ, the same form as the double slit but much sharper
• Rayleigh criterion for a circular aperture: θ = 1.22 λ/D
• Bragg equation for X-ray diffraction from a crystal: mλ = 2d sin θ

Memory Tip: The slit width a controls the big diffraction envelope, while the slit spacing d controls the fine fringes inside it. Think “a for aperture, d for distance between slits.”

Common Mistake: Mixing up a and d. The equation a sin θ = mλ gives dark fringes for one slit, while d sin θ = mλ gives bright fringes for two slits or a grating, even though the two equations look almost identical.

Important Questions:

• How can a single slit produce an interference pattern? Different parts of the slit act like many separate wave sources. Light from these parts travels different distances to a point on the screen and interferes, so the single opening produces a central maximum with weaker side maxima.
• What does the Rayleigh criterion say? Two point sources are just resolvable when the center of one diffraction pattern falls on the first minimum of the other, at θ = 1.22 λ/D. A larger aperture or a shorter wavelength therefore resolves finer detail.

Chapter 5: Relativity

Unit 2: Modern Physics · Difficulty: Hard · Key topics: Einstein’s postulates, simultaneity, time dilation, length contraction, Lorentz transformation, velocity addition, relativistic Doppler effect, momentum, energy

This chapter introduces Einstein’s special relativity of 1905. It starts from two postulates (the laws of physics are the same in every inertial frame, and the speed of light is the same for all observers) and the Michelson-Morley experiment behind them. Simultaneity turns out to be relative, and time dilation (Δt = γΔτ) and length contraction follow, with the twin paradox explained by the traveling twin’s acceleration. The Lorentz transformation replaces the Galilean one, and the velocity-addition rule keeps every speed below c. The chapter finishes with the relativistic Doppler shift, momentum p = γmu, and energy, including E = mc² and E² = (pc)² + (mc²)².

Key Points:

• Postulate 1: the laws of physics are the same in all inertial frames; postulate 2: the speed of light c is the same in all inertial frames
• Lorentz factor: γ = 1/√(1 − v²/c²)
• Time dilation: Δt = γΔτ, where the proper time Δτ is the shortest possible interval between two events
• Length contraction: L = L₀/γ, where the proper length L₀ is the longest possible length
• Relativistic velocity addition means no combination of speeds can exceed c
• Relativistic momentum p = γmu, total energy E = γmc², kinetic energy K = (γ − 1)mc², and rest energy E₀ = mc²

Memory Tip: “Proper” means measured in the frame where the thing is at rest. Proper time is the reading of a clock sitting at the events, and proper length is a ruler at rest with the object. Proper time is always the shortest and proper length always the longest.

Common Mistake: Plugging numbers into the dilation or contraction formulas without first deciding which measurement is the proper one. Identify the rest-frame clock or ruler first, and the formula then follows.

Important Questions:

• A spaceship moves at 0.6c. A clock on board ticks off 10 s. How long does that take as measured from Earth? γ = 1/√(1 − 0.36) = 1.25, so Δt = γΔτ = 12.5 s.
• Why can an object with mass never reach the speed of light? Its relativistic momentum and energy grow without limit as u approaches c, so an infinite amount of work would be needed to accelerate it all the way to c.

Chapter 6: Photons and Matter Waves

Unit 2: Modern Physics · Difficulty: Medium · Key topics: blackbody radiation, Planck’s quanta, photoelectric effect, Compton effect, Bohr model, de Broglie waves, wave-particle duality, uncertainty principle

Here the book collects the experiments that classical physics could not explain. Blackbody radiation (Wien’s displacement law and Stefan’s law) leads to Planck’s idea that energy is exchanged in discrete quanta. The photoelectric effect, with its cut-off frequency, then shows light behaving as photons, and Compton scattering confirms that photons carry momentum. Bohr’s three postulates explain the hydrogen spectrum and the Rydberg formula. De Broglie’s matter waves, confirmed by the Davisson–Germer electron diffraction experiment, complete the picture of wave-particle duality and lead to the Heisenberg uncertainty principle.

Key Points:

• Wien’s law: the hotter the body, the shorter the wavelength of its emission peak; Stefan’s law: radiated power is proportional to T⁴
• Planck: radiation and cavity walls exchange energy only in quanta; a photon’s energy depends only on its frequency
• Photoelectric effect: K_max = hf − φ, with no emission below the cut-off frequency however intense the light
• Compton effect: scattered X-rays have a longer wavelength because each photon gives momentum to an electron
• Bohr’s postulates: circular orbits, quantized angular momentum, and photon emission or absorption at each quantum jump
• De Broglie: every particle with momentum is also a wave, with λ = h/p

Memory Tip: In the photoelectric effect, frequency decides whether and intensity decides how many. Frequency sets the energy of each photon, which determines if an electron can escape at all, while intensity only sets the number of photons and so the number of electrons.

Common Mistake: Thinking that a bright enough beam of low-frequency light will eventually eject electrons. Below the cut-off frequency no single photon has enough energy, so no amount of brightness helps.

Important Questions:

• Why can classical wave theory not explain the photoelectric effect? It predicts that a bright enough beam of any frequency should eject electrons, with energy growing with intensity and a delay at low intensity. Experiments show a cut-off frequency, electron energies independent of intensity, and instant emission. Only the photon picture fits.
• How does the de Broglie wavelength of a particle depend on its momentum? λ = h/p, so it is inversely proportional to the momentum. For everyday objects the momentum is so large that the wavelength is far too small to detect.

Chapter 7: Quantum Mechanics

Unit 2: Modern Physics · Difficulty: Hard · Key topics: wave functions, probability density, uncertainty principle, Schrödinger equation, particle in a box, quantum harmonic oscillator, tunneling

This is where the book builds actual quantum mechanics. A system’s state is described by a wave function, and in Born’s interpretation its square gives the probability density, so wave functions must be normalized. The Heisenberg uncertainty principle then comes from the wave nature of matter. The Schrödinger equation is introduced and used on three model systems: the particle in a box (quantized energies indexed by a quantum number), the quantum harmonic oscillator (evenly spaced levels and a nonzero ground-state energy), and tunneling through a finite barrier, which has no classical analog and underlies radioactive decay and the scanning tunneling microscope.

Key Points:

• The square of the wave function is the probability density of finding the particle near a given location
• Wave functions must be normalized before use; the expectation value is the average value of a quantity
• Uncertainty principle: Δx Δp ≥ ℏ/2, and the limit comes from wave nature, not from poor instruments
• For a time-independent potential, a solution of the Schrödinger equation is a spatial wave function multiplied by a time-modulation factor
• Particle in a box: the wave function must vanish at the walls, so energies are quantized and labeled by a principal quantum number
• Quantum oscillator: evenly spaced energy levels and a ground-state energy above zero, so it is never at rest
• Tunneling probability depends exponentially on barrier width, so small changes in width cause large changes in transmission

Memory Tip: A particle in a box behaves like a guitar string pinned at both ends: only wave patterns that fit a whole number of half-wavelengths into the box survive, and that is exactly why only certain energies are allowed.

Common Mistake: Treating the wave function itself as a probability. The probability density is the square of the wave function (its squared magnitude), and the wave function can even be a complex number.

Important Questions:

• What does Born’s interpretation say about the wave function? The square of the wave function at a point gives the probability density of finding the particle around that point. That is why the total probability over all space must equal one, which is the normalization condition.
• Why can a quantum harmonic oscillator never have zero energy? Its ground-state energy is above zero. Sitting perfectly still at the bottom of the well would fix both position and momentum exactly, which the uncertainty principle forbids, so the oscillator always has quantum fluctuations.

Chapter 8: Atomic Structure

Unit 2: Modern Physics · Difficulty: Hard · Key topics: hydrogen atom, quantum numbers, orbital magnetic moment, electron spin, Pauli exclusion principle, periodic table, atomic spectra and X-rays, lasers

The chapter applies the Schrödinger equation to the hydrogen atom, where the electron’s state is given by quantum numbers (n, l, m) and predictions are statements of probability rather than Bohr orbits. Because the orbiting electron acts like a current loop, it has a magnetic moment, and an external field splits energy levels. Electron spin adds a fifth quantum number and explains fine and hyperfine structure. Pauli’s exclusion principle then builds the periodic table from electron configurations. The chapter ends with atomic spectra and X-ray production, and with lasers, whose coherent light depends on population inversion.

Key Points:

• The state of the electron in hydrogen is specified by the quantum numbers n, l and m; spin adds s and m_s, making five in total
• The Schrödinger model predicts probabilities, unlike the definite orbits of the Bohr model
• The electron’s orbital motion makes a magnetic dipole moment, and an external magnetic field splits the energy levels
• Electron spin quantum number is ½, and m_s = +½ or −½ (spin up or spin down)
• Pauli exclusion principle: no two electrons in an atom can have all the same quantum numbers
• X-ray photons are produced when an outer-shell electron fills an inner-shell vacancy, and their frequency depends on the atomic number Z
• Laser light is coherent and monochromatic, produced by population inversion followed by de-excitation

Memory Tip: Treat the quantum numbers as an address: n is the building (the shell and its energy), l is the floor (the subshell), m is the room (its orientation) and m_s is which of the two beds you take (spin up or down). Pauli’s rule says no two electrons share the same full address.

Common Mistake: Picturing the electron as a tiny ball circling the nucleus on a track, as in Bohr’s model. In the Schrödinger picture the electron is described by a probability distribution around the nucleus, not a path.

Important Questions:

• For the principal quantum number n = 3, what values can the orbital quantum number l take? l can be 0, 1 or 2, that is, any whole number from 0 up to n − 1.
• What does the Pauli exclusion principle say, and why does it matter for the periodic table? No two electrons in an atom can share the same set of quantum numbers. Electrons therefore fill shells and subshells one after another, and the resulting electron configurations explain the structure of the periodic table.

Chapter 9: Condensed Matter Physics

Unit 2: Modern Physics · Difficulty: Medium · Key topics: ionic and covalent bonds, molecular spectra, crystal structures, free electron model, band theory, semiconductors and doping, diodes and transistors, superconductivity

This chapter scales quantum mechanics up from atoms to molecules and solids. It compares ionic bonds (an electron is transferred) with covalent bonds (electrons are shared, with space-symmetric wave functions and hybridization), then shows that molecular vibrational and rotational levels produce absorption spectra with selection rules. For solids it covers FCC and BCC packing in ionic crystals, the free electron model of metals with its Fermi energy, and band theory, where energy bands and gaps decide conduction. Doping, the Hall effect, diodes and transistors follow, and the chapter ends with superconductivity and Cooper pairs.

Key Points:

• Ionic bonds transfer an electron between atoms; covalent bonds share electrons
• Vibrational energy spacings in a molecule are larger than rotational ones, and transitions obey selection rules
• In a metal at T = 0, electrons fill levels from the bottom up, and the highest filled level is the Fermi energy
• Solids have continuous energy bands separated by gaps, and this structure decides whether a solid conducts
• n-type doping adds levels just below the conduction band; p-type doping adds levels just above the valence band
• A diode (n-p junction) passes current in one direction; a transistor (n-p-n junction) acts as an electric valve controlling a current
• A superconductor has zero electrical resistance and repels magnetic field lines, and it is explained by Cooper pairs

Memory Tip: n-type means negative carriers, because the donated extra electrons sit just below the conduction band. p-type means positive carriers (holes), because the new levels sit just above the valence band.

Common Mistake: Assuming the electrons in a metal have almost no energy at absolute zero. Because of the exclusion principle they must pile up into higher and higher levels, so they have very large energies even at T = 0 K.

Important Questions:

• What is the Fermi energy? It is the energy of the highest occupied level when electrons fill the allowed states of a metal from lowest to highest at T = 0 K, with two electrons (spin up and spin down) per level.
• How does band theory separate conductors, semiconductors and insulators? It depends on the energy bands and gaps. A conductor has a partly filled band, a semiconductor has a small gap above a filled band, and an insulator has a large gap.

Chapter 10: Nuclear Physics

Unit 2: Modern Physics · Difficulty: Medium · Key topics: nuclear properties, binding energy, radioactive decay, alpha/beta/gamma decay, fission, fusion, medical uses and biological effects

The chapter looks inside the nucleus. It defines atomic number Z, neutron number N, mass number A and isotopes, then explains mass defect and binding energy and the binding-energy-per-nucleon curve, which shows why both splitting and combining nuclei can release energy. Radioactive decay is treated through the decay constant, half-life and the law N = N₀e^−λt, with carbon-14 dating as the main application. Alpha, beta and gamma decay and decay series come next. Fission and its breeder reactors, fusion and the Q value, and the medical and biological effects of radiation complete the chapter.

Key Points:

• A nucleus has Z protons and N neutrons, with mass number A = Z + N; isotopes share Z but differ in N
• Mass defect is the nucleus’s mass deficit compared with its separate nucleons, and binding energy equals the mass defect times c²
• The binding-energy-per-nucleon curve shows that dividing heavy nuclei or combining light ones releases energy
• Radioactive decay law: N = N₀e^−λt; a large decay constant means a short half-life
• Alpha decay reduces A by 4 and Z by 2; beta decay emits an electron or a positron; gamma decay emits a photon from an excited nucleus
• Carbon-14 dating compares the abundance of ¹⁴C in an artifact with its abundance in living tissue
• Fusion of light nuclei releases energy and powers the Sun; ionizing radiation harms cells by disrupting reproduction and function

Memory Tip: Think of the binding-energy-per-nucleon curve as a hill whose peak is near iron. Light nuclei fuse and heavy nuclei split because each moves toward the peak, and the energy released is the climb.

Common Mistake: Believing that everything has decayed after two half-lives. Each half-life removes half of what is left, so after n half-lives a fraction (½)ⁿ of the sample remains.

Important Questions:

• A sample has a half-life of 5 years. What fraction remains after 15 years? Fifteen years is three half-lives, so (½)³ = 1/8 of the original sample remains.
• Why do both nuclear fission and nuclear fusion release energy? On the binding-energy-per-nucleon curve, medium-mass nuclei are the most tightly bound. Splitting a heavy nucleus or fusing light nuclei both produce more tightly bound nuclei, and the difference in binding energy is released.

Chapter 11: Particle Physics and Cosmology

Unit 2: Modern Physics · Difficulty: Medium · Key topics: fundamental forces, quarks and leptons, conservation laws, accelerators and detectors, Standard Model, Big Bang, early universe

The final chapter runs from the smallest particles to the whole universe. It ranks the four fundamental forces, sorts elementary particles into fermions and bosons, and splits matter into quarks and leptons in three-member families with antiparticles. Conservation laws (baryon number, lepton numbers, strangeness) decide which reactions are allowed. The six quarks build baryons and mesons. The book then describes accelerators and detectors, the Standard Model with Feynman diagrams and force-carrying bosons, and grand unified theories. The last two sections cover Hubble’s expansion of the universe, the Big Bang, and the cosmic microwave background as evidence for a hot, dense early universe.

Key Points:

• The four fundamental forces, from strongest to weakest: strong nuclear, electromagnetic, weak nuclear and gravitational
• Fermions have half-integer spin and obey the exclusion principle; bosons have integer spin and carry the forces
• Quarks feel the strong force and leptons do not; the six quarks are up, down, charm, strange, top and bottom
• Baryons contain three quarks and mesons contain a quark and an antiquark; quarks cannot exist in isolation
• Baryon number and the three lepton numbers are conserved in all processes; strangeness is conserved only in strong and electromagnetic interactions
• A Feynman diagram shows particle interactions on a space-time graph
• Distant galaxies recede at speeds proportional to their distance; the book quotes about 70 km/s/Mpc and a Big Bang about 13.7 billion years ago (2016-era figures)

Memory Tip: Fermions build matter and bosons carry forces. Electrons and quarks are fermions that make up atoms, while a force such as electromagnetism is passed between them by bosons.

Common Mistake: Imagining the Big Bang as an explosion of matter into empty space. The book’s picture is an expanding universe, like dots on an inflating balloon, where every point moves away from every other point.

Important Questions:

• What is the difference between a baryon and a meson? A baryon is made of three quarks, while a meson is made of one quark and one antiquark.
• Using a Hubble constant of 70 km/s/Mpc, how fast is a galaxy 100 Mpc away receding? v = H₀d = (70 km/s/Mpc)(100 Mpc) = 7,000 km/s.

Download University Physics Volume 3 PDF (Free)

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How to Study This Book

This is the third volume of a calculus-based sequence, so it assumes the earlier volumes. Chapter 1 leans on the electromagnetic waves covered at the end of Volume 2, and the wave ideas from Volume 1 (superposition, wavelength, frequency) run through all of Unit 1. Chapter 5 builds on Newtonian momentum and the work-energy theorem, so refresh those first if they feel rusty.

Chapters 1–4 (Unit 1: Optics) are best read in order. Chapter 1 is the gentlest, because Snell’s law, total internal reflection and polarization are used everywhere afterward. Chapter 2 is the most formula-heavy and sign-convention-heavy chapter of the unit, so practice drawing ray diagrams rather than only substituting into the mirror and lens equations. Chapters 3 and 4 are the wave-optics pair; keep a clear note of when d (slit spacing) and a (slit width) appear.

Chapter 5 (Relativity) is largely self-contained and can be read on its own, but read its nine sections in order, because the Lorentz transformation in 5.5 is the foundation for velocity addition, the Doppler effect, momentum and energy in 5.6–5.9.

Chapters 6–8 are the quantum core, and this is where most of your study time should go. Chapter 6 builds the experimental case, Chapter 7 is the mathematical turning point (wave functions, uncertainty and the Schrödinger equation), and Chapter 8 applies it to the hydrogen atom and the periodic table. If your syllabus is short, protect these three chapters first.

Chapters 9–11 are applications and surveys built on that core. Chapter 9 uses the Pauli exclusion principle from Chapter 8 to explain metals and semiconductors. Chapter 10 is the most calculation-friendly chapter in the book thanks to the decay law and binding energies. Chapter 11 is mostly conceptual and ends with cosmology, where the book’s figures (about 70 km/s/Mpc and 13.7 billion years) are from 2016; current measurements put the age at about 13.8 billion years and the Hubble constant at roughly 67 to 73 km/s/Mpc, so use your lecturer’s numbers in exams.

Know what the book does not do: it is not a full quantum mechanics course (expect a dedicated course in your BS Physics program to go much deeper), and it only touches general relativity as a contrast to special relativity. Thermodynamics, electricity and mechanics belong to the other two volumes. After every chapter, use the Key Equations page as a one-page revision sheet.

Used In These Programs

This book is used for the Modern Physics course in: BS Physics. Browse all Modern Physics books or all Physics category books.

Who Should Read This

University Physics Volume 3 is written for BS Physics and engineering students who have finished the mechanics and electromagnetism volumes and are ready for optics, relativity and quantum physics. Like the earlier volumes it uses calculus in its derivations, so integration and differentiation should be comfortable. It suits students who learn from worked examples before attempting problems, and it is a good first pass at quantum ideas before a dedicated quantum mechanics course. If you are coming straight from FSc, the Physics First Year (Class 11) book introduces physical optics and special relativity at intermediate level, and the Physics 2nd Year FSC book covers the Dawn of Modern Physics, atomic spectra and nuclear physics, which makes a useful warm-up for Chapters 5, 6, 8 and 10.

Applicable Universities

This book is useful for students at Pakistani universities offering BS Physics or engineering programs, including Punjab University, Virtual University, COMSATS, FAST, UET, NUST, GIKI, and other HEC-recognized institutions, wherever a calculus-based course in optics and modern physics is part of the degree.

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Related Books

• Physics 2nd Year FSC (Punjab Board) – atomic spectra, solids, and nuclear physics at intermediate level
• Physics First Year (Class 11) FSc – physical optics and special relativity basics
• Calculus Volume 1 – OpenStax (the differentiation you will use)
• Calculus Volume 2 – OpenStax (the integration behind wave functions and probability)

University Physics Volume 3 gives BS Physics students a full, free route from lenses and interference to relativity, quantum mechanics, nuclei, and the Big Bang. Browse more Physics books or Mathematics books for the rest of your semester.

University Physics Volume 3, by Samuel J. Ling, Jeff Sanny, William Moebs (senior contributing authors), and contributing authors. OpenStax, Rice University. Free under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 licence. Access for free at https://openstax.org/details/books/university-physics-volume-3