What is Modern physics: Definition and 253 Discussions

Modern physics is a branch of physics either developed in the early 20th century and onward or branches greatly influenced by early 20th century physics. Notable branches of modern physics include quantum physics, special relativity, and general relativity.
Classical physics is typically concerned with everyday conditions: speeds are much lower than the speed of light, sizes are much greater than that of atoms, and energies are relatively small. Modern physics, however, is concerned with more extreme conditions, such as high velocities that are comparable to the speed of light (special relativity), small distances comparable to the atomic radius (quantum mechanics), and very high energies (relativity). In general, quantum and relativistic effects are believed to exist across all scales, although these effects may be very small in everyday life. While quantum mechanics is compatible with special relativity (see relativistic quantum mechanics), one of the unsolved problems in physics is the unification of quantum mechanics and general relativity, which the Standard model (of particle physics) currently cannot account for.

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  1. F

    Why Does Cramster Simplify Velocity Components Incorrectly in Physics Problems?

    Homework Statement This problem is from Modern Physics by Kenneth Krane 2nd ED The problem is: An atom of mass m moving in the x direction with speed v collides elastically with an atom of mass 3m at rest. After the collision the first atom moves in the y direction. Find the direction of...
  2. D

    Modern Physics Question: Corrected potential for NaCl

    Homework Statement The potential energy "V" of NaCl can be described empirically by: V = -(e2/(4*Pi*epsilon)) + A*exp[-R/rho] where R is the internuclear separation. The equilibrium separation of the nuclei Ro is 2.4 Angstroms and the dissociation energy is 3.6 eV. a) Calculate A and...
  3. J

    Exploring Gravity: Other Theories in Modern Physics

    Is there any other formally considered theories relating to the operations of gravity other than relativity? They must still be considered in modern physics. If so could one point me in the direction.
  4. F

    Modern Physics - Length of infinite well that has an electron

    Homework Statement ** My book doesn't have any solutions in the back , and I trying to find out if I am doing the problems correctly. My book is Modern Physics for Scientists and Engineers by John C. Morrison. If you know anywhere I can find the Answers. I would greatly appreciate it! The...
  5. F

    Modern Physics Introduction Photon Energy and Wavelength

    Homework Statement Suppose that a beam of light consists of photons having an energy of 5.4 eV. what is the wavelength of the light? Homework Equations hc = 1240 eV*nm E = \frac{hc}{\lambda} The Attempt at a Solution 5.4eV = \frac{1240eV*nm}{\lambda} \lambda =...
  6. F

    Modern Physics Introduction Standing Wavelength and Frequency

    Homework Statement Find the length of the smallest standing wave that can be formed with light having a frequency of 600THZ. Homework Equations f = 600*10^{12}Hz c = 2.998x10^{8}\frac{m}{s} \lambda f=c The Attempt at a Solution \lambda f=c \lambda...
  7. F

    Modern Physics Introduction Question on Electron Speed and Momentum

    Homework Statement Suppose that an electron has a kinetic energy of 1.0 eV. What are the speed and the momentum of the electron? The book is Modern Physics for Scientists and Engineers by Morrison. If anyone knows where to get any of the answers(or solutions. solutions may be harder to...
  8. P

    Scanning Tunneling Microscope Question (introductory modern physics)

    Homework Statement A scanning tunneling microscope (STM) can precisely determine the depths of surface features because the current through its tip is very sensitive to differences in the width of the gap between the tip and the sample surface. Assume that in this direction the electron wave...
  9. R

    Modern Physics: Current in Wolfram Filament

    Homework Statement Determine the current in the wolfram filament with the diameter 0.8 mm and the temperature T=2800K, which is maintained constant. Specific electrical resistance of the filament is ρ = 0.92⋅10-4Ohm⋅cm. The temperature of environment is t = 17C. Homework Equations...
  10. N

    Prerequisites for modern physics

    What is needed from basic physics to study modern physics ?
  11. D

    Looking for a textbook/lecture series for modern physics

    Apparently my college doesn't offer the same intro physics courses in both semesters, and they suggest that physics majors take physics starting in their first year. Well, I never really considered being a physics major and opted to have a more liberal curriculum my first semester. It's kind of...
  12. A

    Asking for advices on assigned textbook on modern physics

    I am going to take an intro modern physics course which includes these topics in syllabus: -intro to relativity & quantum theory -Schroedinger equation -particle/wave duality -statistical physics: Bose and Fermi distribution My assigned textbook is Concepts of Modern Physics by Arthur...
  13. M

    How Does Changing the Work Function Affect Photoelectron Emission?

    Modern Physics, homework, please help:( A metal surface with a work function of (W1=3eV) is illuminated with a monochromatic ultraviolet light of frequency v*1. The maximum speed of the ejected photo electrons was found to be v1=0.6x10^6m/s. a) compute the wavelength λ of the incident...
  14. C

    Topics in modern physics class

    What topics are typically covered in a 300 level modern physics class?
  15. D

    Reviewing Mechanics & EM for Modern Physics: Priority Topics

    I'm taking Modern Physics in the spring semester (starts Jan 10). It's been over 5 years since I took Mechanics and EM. Which topics from these courses should I review in preparation for Modern Physics? I plan to review everything, however this will take me longer than the time available before...
  16. D

    Preparing for Modern Physics: Mechanics & EM Review

    I'm taking Modern Physics in the Spring semester (starts Jan 10). It's been over 5 years since I took Mechanics and EM. Which topics from these courses should I review in preparation for Modern Physics? I plan to review everything, however this will take me longer than the time available...
  17. S

    Exploring E/M: Modern Physics and Its Importance

    What is importance of finding E/M? I am doing a project on E/M and helmholtz coil. I heard that E/M is beginning of the Modern Physics. Can you tell me more about this experiment and why is it so important to know this ratio? I also want to be refereed to some sources in which i can get whole...
  18. fluidistic

    Modern physics, Bohr model of atom

    Homework Statement According to Bohr's atomic model, 1)Determine the allowed radius of the orbit of the electrons. Calculate the radius of the first orbit for the hydrogen atom. 2)Show that the energy of the electron is quantized. Calculate the energy corresponding to an electron on the first...
  19. B

    Modern Physics I: Find Energy Loss & Wavelength

    Homework Statement An electron with energy 10^3 MeV collides with a photon whose wavelength corresponds to the maximum wavelength of the 2.7-K cosmic background radiation. What is the maximum energy loss the electron can suffer as a result of the collision? What is the wavelength of the photon...
  20. M

    Modern Physics I: Find time from energy

    Homework Statement A particle with a rest energy of 2400 MeV has an energy of 15 GeB (15x10^9 eV). Find the time in Earth's frame of reference necessary for this particle to travel from Earth to a star four light-years distant. Homework Equations The Attempt at a Solution I...
  21. B

    Modern Physics: Finding pressure using energy.

    Homework Statement A beam of pions (\pi-mesons, with rest energy m\pi c2=140 MeV) consisting of 1010 pions/cm^2s moves with speed such that the total energy of each pion is 10^5 MeV. What is the pressure the beam exerts on a surface that absorbs it and brings it to rest? Please note: For...
  22. D

    Physics for Scientists and Engineers vs with Modern Physics

    Physics for Scientists and Engineers vs "" with Modern Physics Would anyone know if there is a difference between the two books off the top of their head? LINK: https://www.amazon.com/dp/0495827819/?tag=pfamazon01-20 LINK: https://www.amazon.com/dp/1439048444/?tag=pfamazon01-20 I mean one...
  23. E

    Need Modern Physics Formula sheet

    Hello, I am attending the Modern Physics class at my college, and I am struggling to process all of the information the instructor is presenting. Part of that confusion stems from this being a summer course, the other part is from the sheer lack of organization. One second were deriving a...
  24. A

    Axiomatic Systems & Modern Physics

    Hi, I'm not sure if this is the right place to post this. Are other different axiomatic systems used for QM & GR? I mean, as I'm currently a high school student, all theorems I've learned are proved by the same set of axioms. I wonder if another applicable axiomatic system is used for...
  25. H

    Exploring Modern Physics: Must-Have Books for Enthusiasts

    I am a physics enthusiast and want to acquire as much knowledge in this area (I am in penultimate year of high school in Romania and want to continue with a college physics, but until then try to learn as much as possible). I want to know more about modern physics (relativity, quantum...
  26. Shackleford

    So, I my Modern Physics I grade was finally posted this morning.

    Well, I was hoping for an A- :frown:, because I thought my exam grades (22/25, 20/25, 22/25) might have warranted it even though my homework average (maybe 40/50) wasn't that great. Actually, now that I'm looking at it, it seems it was a pretty rigid grade and there probably wasn't much "curve,"...
  27. I

    I need some Modern physics text book suggestion

    Hi I am in my freshmen year and I am taking a course on Modern Physics. We use the book "Concept of Modern Physics" by Arthur Beiser. I have huge problem understanding the wave and particle dual properties of matter. And now we are about to start Quantum Mechanics. it seems further...
  28. Shackleford

    How to Tackle Quantum Mechanics Integrals for Modern Physics Exam?

    URGENT HELP NEEDED - Last Modern Physics I exam tomorrow I've done reasonably well in the class so far. However, I have not done well since starting modern quantum mechanics. The last several problem sets have covered quantum mechanics, and I failed Problem Set 6. I've never failed anything in...
  29. T

    Nuclear Model - Expression for Total Energy [Modern Physics]

    Homework Statement Derive an expression for the total energy required to asemble a sphere of charge corresponding to a nucleus of atomic number Z and radius R. Assume the nucleus is a sphere of uniform volume charge density \rho Homework Equations \rho = mass / volume = 3Am / 4*pi*R3...
  30. P

    Modern Physics - Extention of the Lorentz Transformation?

    Homework Statement Conventionally, the Lorentz Transformation relates two reference frames that begin at the same location and time with one reference frame moving at a constant velocity {\vec{v}} along a positive {x}-axis (which is common to both reference frames) with respect to the other...
  31. I_am_learning

    The Debate Around Arthur Beiser's Modern Physics Theory

    Arthur Beiser in His Modern Phyics books, says that there is absoluteness of past and future. If Event 1 occurs after event 2 in a given frame of reference, Then same sequence occurs in very other frame of reference. Thats not always true, isn't it?
  32. R

    Phase velocity wave packets Modern Physics

    Homework Statement The phase velocity of each wavelength of white light moving through or- dinary glass is a function of the wavelength i.e. glass is a dispersive medium. What is the general dependence of phase velocity on wavelength in glass? Is dvp/dlamda positive or negative? Why...
  33. P

    Modern Physics - Invariability of Newton's 2nd Law under a GT?

    Homework Statement Show that the form of Newton's Second Law is invariant under: (a). a Galilean Transformation (GT) in 1-Dimension. (b). a Galilean Transformation (GT) in 2-Dimensions. (c). a Galilean Transformation (GT) in 3-Dimensions. Homework Equations Newton's Second Law...
  34. ZapperZ

    Teaching and understanding of quantum interpretations in modern physics courses

    It took me a while to finish reading http://prst-per.aps.org/abstract/PRSTPER/v6/i1/e010101" {you can get free access to the paper}, and I still don't have a clear idea of it rather than the conclusion that stated that if the instructor doesn't make any explicit discussion on the interpretation...
  35. W

    What is the stopping potential for a wavelength of 230nm?

    Modern Physics question! Homework Statement When radiation of wavelength 350nm is incident on a surface, the maximum kinetic energy of the photoelectrons is 1.2ev. What is the stopping potential for a wavelength of 230nm? Homework Equations \phi=hc/\lambda-eV0( V0= V 'nought') I am...
  36. P

    Modern Physics - Extension of the Galilean Transformation?

    Homework Statement Conventionally, the Galilean Transformation relates two reference frames that begin at the same location and time with one reference frame moving at a constant velocity {\vec{v}} along a positive {x}-axis (which is common to both reference frames) with respect to the other...
  37. S

    Modern Physics vs Classical Physics

    Just curious, what's the difference? I was told be someone that modern physics has ways of accurately defining what a force is, while classical physics does not define forces, only acceleration in terms of force and mass. Again, just curious.. What are the major differences? Is one wrong...
  38. L

    Is there a video lecture on modern physics coordinates?

    http://i46.tinypic.com/r9ha92.jpg it looks like a coordinate i don't know what is the meaning of this thing ?
  39. Shackleford

    What to brush up on? Modern Physics I and Vector Analysis

    I'm taking these next semester. I'm taking Differential Equations right now, so I'll have that under my belt.
  40. N

    Resolves the issue of free will as brought forth by modern physics

    I was wondering if anyone can provide me with literature that resolves the issue of free will as brought forth by modern physics, ie. the fact that atomic processes cannot be fully determined. Thank you for your concern,
  41. J

    Modern Physics, The Observer, and free-will

    Hello, First off, I would like to say thank you for being of much help as I browsed these forums a little and gained some information. Second, I would like to say that at this in point of time my understanding of Physics is limited, so I do not intend to put myself across as...
  42. T

    Can someone point me to some good online resources about Modern Physics?

    Here's the description of a class I'm taking next semester: Electrons, protons, and structure of matter: a historic view. The Rutherford-Bohr atom and elements of quantum mechanics and their applications to atomic, nuclear, and solid state physics. Usually offered every spring. Prerequisite...
  43. O

    Can You Solve This AP Physics B Photoelectric Effect Problem?

    1.Question Its due tommorow and its a former AP Physics B free response questions. I appreciate any help. It comes with a diagram which I had to put in a different link. Diagram: http://img.photobucket.com/albums/v3...1/physics1.jpg Question: Electromagnetic radiation is incident on...
  44. S

    What is a good introductionary textbook for modern physics?

    What is a good introductionary textbook for "modern physics?" I am looking for a decent introductionary textbook to the various topics that get introduced in the first course after the classical mechanics(ie. a textbook targeted towards the student typically in the 4th semester in an undergrad...
  45. N

    General Modern Physics questions

    In my modern physics course we learn that different atoms and molecules have a unique set of allowed orbitals where it's electrons are allowed to exist. We then talk about how this corresponds to unique spectral lines emitted and absorbed by the different atoms/molecules. This continues onto...
  46. D

    Need a topic for paper in modern physics

    I am writing a paper on a "modern" modern physics experiment and need some help on finding a subject to write about. Any help on finding a topic would be greatly appreciated. Thank you in advance.
  47. D

    Need a topic for paper in modern physics

    I am writing a paper on a "modern" modern physics experiment and need some help on finding a subject to write about. Any help on finding a topic would be greatly appreciated. Thank you in advance.
  48. U

    Modern Physics Exam: Difficulties Solving Problems? Get Help Here!

    hello everybody . i have an exam in modern physics ,about relativistic kinematics and relativistic dynamics and quantum effects . but i have some difficulties when solving problems and i'd like to work it more . so if anyone knows an interesting link or a free ebook where i can find solved...
  49. X

    What is the work function of the metal?

    Light of 300 nm wavelength strikes a metal plate, and photoelectrons are produced moving as fast of 0.002c. What is the work function of the metal?
  50. R

    Angular Momentum (Modern Physics)

    Homework Statement This problem is giving me a headache and unfortunately I can't find any example that is similar to it. A hydrogen atom is in the n = 3, l = 2 state. (a) What are the possible values of j? (b) What are the possible values of the magnitude of the total angular momentum...
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