em wave

Physics 242
General Physics II

Dr. Tom Sandin
Professor Emeritus

Office: Marteena 308B

Office Hours: MWR 12-3 or
by appointment

Tel: (336)285-2124
Fax: (336)256-0815
sandint@ncat.edu

To view the documents on this page, you may need Adobe Acrobat Reader.
To download a free copy of Adobe Reader, click on the icon ->

  • This semester's syllabus
  • Final Exams, December 5 and 6, 1-3 pm

  • Final Exam Information Sheet
  • EXTRA CREDIT LECTURES

    For ten points each day: simply arrive on time in 312 Marteena and take notes for fifty minutes. (I'll hand back your notes with their points when you hand in your final exam.)

  • Monday, November 21 at 8 AM or 9 AM: Relativity (completed)
  • Monday, November 28 at 8 AM or 9 AM: Quantum Phenomena (completed)
  • Wednesday, November 30 at 8 AM or 9 AM: Nuclear and Particle Physics (completed)
  • Block 12

  • Block 12 Notes
  • Block 12 Objectives
  • Block 12 Drill Set
  • Block 11

  • Block 11 Notes
  • Block 11 Objectives
  • Block 11 Drill Set
  • Block 10

  • Block 10 Notes
  • Block 10 Objectives
  • Block 10 Drill Set
  • Block 9

  • Block 9 Notes
  • Block 9 Objectives
  • Block 9 Drill Set
  • Block 8

  • Block 8 Notes
  • Block 8 Objectives
  • Block 8 Drill Set
  • Click here to see a V E R Y S L O W linearly-polarized electromagnetic wave animation.

    Doppler Effect: animated GIFs by Professor Emeritus Martha Takats

    First click for the case when the source is at rest: Click here.
    Then click for the case when the source is moving: Click here.

    DOPPLER EFFECT SIGNS TUTORIAL

    A source (S) of sound and a listener (L) both move along an east-west (E-W) line.
    Find the signs of the velocity components of L and S.

    1. If both move west (left) with the source leading. Click on one below.

    Both +     + for L, - for S     - for L, + for S     Both -

    2. If both move west (left) with the listener leading. Click on one below.

    Both +     + for L, - for S     - for L, + for S     Both -

    3. If the source moves east (right) toward the listener moving west (left). Click on one below.

    Both +     + for L, - for S      - for L, + for S     Both -

    4. If the source moves east (right) away from the listener moving west (left). Click on one below.

    Both +     + for L, - for S     - for L, + for S     Both -

    Strongly recommended by PHYS 242 students to learn a right-hand rule:
    Try these movies first.
    If the movies don't run on your computer, use these animated GIFs.

    Block 7, Part 2

  • Block 7, Part 2, Notes
  • Block 7, Part 2, Objectives
  • Block 7, Part 2, Drill Set
  • Block 7, Part 1

  • Block 7, Part 1, Notes
  • Block 7, Part 1, Objectives
  • Block 7, Part 1, Drill Set
  • Transverse and Longitudinal Mechanical Traveling Waves
    Animated GIFs by Professor Emeritus Martha Takats, Ursinus College


    The animation below shows a transverse wave on a string. The wave itself moves to the right, but the individual particles of the string, such as those indicated by red and blue squares, move up and down (perpendicular to the direction the wave moves). To show that the red and blue squares really do move only up and down (not right or left), position the cursor just below any one of them.



    This second animation represents a longitudinal wave, such as a sound wave in air. The vertical lines represent particles of the medium (every tenth vertical line is made boldface). This longitudinal wave moves to the right, as you can see by noting that any region of compression (where the particles are close together) gradually moves to the right. But each individual particle moves back and forth along the direction the wave moves. (The animation ignores the very rapid, but random, thermal motion of the particles.)




    A Demonstration of Standing Waves Animated GIFs by Professor Emeritus Martha Takats



    The red traveling wave and the blue traveling wave on the string are identical transverse waves, except the red wave moves to the right while the blue wave moves to the left.
    The white transverse standing wave is the sum of the red and blue traveling waves.



    Only the transverse standing wave is shown below. Note that at some points (the nodes) the particles of the string don't move at all while at other positions (the antinodes) they move the most.

    The red and blue squares are NOT at nodes or antinodes.
    However, each red square is one wavelength from its adjacent red square(s), so the red squares all move together in phase.
    How far apart are adjacent blue squares? How do the blue squares move relative to one another?
    How far is each blue square from its nearest red square(s)? As a result, how do the blue squares move relative to the red squares?



    The vertical lines below represent particles in a longitudinal standing wave (every tenth line is bolder). Can you locate the nodes and antinodes?
    In terms of the wavelength, how far is each of the bolder vertical lines from its adjacent bolder vertical line(s)? Therefore, how do these lines move relative to one another?




    Block 6

  • Block 6 Notes
  • Block 6 Objectives
  • Block 6 Drill Set
  • Block 5

  • Block 5 Notes
  • Block 5 Objectives
  • Block 5 Drill Set
  • Strongly recommended by PHYS 242 students to learn a right-hand rule:
    Try these movies first.
    If the movies don't run on your computer, use these animated GIFs.

    Block 4

  • Block 4 Notes
  • Block 4 Objectives
  • Block 4 Drill Set
  • Strongly recommended by PHYS 242 students to learn a right-hand rule:
    Try these movies first.
    If the movies don't run on your computer, use these animated GIFs.

    Block 3

  • Block 3 Notes
  • Block 3 Objectives
  • Block 3 Drill Set
  • Block 2

  • Block 2 Notes
  • Block 2 Objectives
  • Block 2 Drill Set
  • Block 1, Part 2

  • Block 1, Part 2 Notes
  • Block 1, Part 2 Objectives
  • Block 1, Part 2 Drill Set
  • Block 1, Part 1

  • Block 1, Part 1 Notes
  • Block 1, Part 1 Objectives
  • Block 1, Part 1 Drill Set
  • DIRECTIONS TUTORIAL

    1. A positive point charge is directly above another positive point charge.

    +

    +

    Both are in the plane of the screen.
    What direction is the force exerted on the upper positive charge by the lower positive charge?
    left right toward the top toward the bottom into the screen out of the screen UNDETERMINED NONE
    (You should understand why the direction is the same if both charges were negative.)

    2. A positive point charge is directly above a negative point charge.

    +

    -

    Both are in the plane of the screen.
    What direction is the force exerted on the upper positive charge by the lower negative charge?
    left right toward the top toward the bottom into the screen out of the screen UNDETERMINED NONE
    (You should understand why the direction is the same if their charges were exchanged.)

    3. An external electric field exerts a force toward the top of the screen on an electron. What is the direction of that electric field?
    left right toward the top toward the bottom into the screen out of the screen UNDETERMINED NONE

    4. An external electric field directed to the left exerts a force on a proton. What is the direction of that force?
    left right toward the top toward the bottom into the screen out of the screen UNDETERMINED NONE

    5. A positive charge is directly in front of you in the plane of the screen. Point P is on a line between the charge and you. (The line is perpendicular to the screen.) At point P, what is the direction of the electric field set up by that positive charge?
    left right toward the top toward the bottom into the screen out of the screen UNDETERMINED NONE

    6. A different point P is to the left of a negative charge.   P·                -
    Both are in the plane of the screen.
    At that different point P, what is the direction of the electric field set up by that negative charge?
    left right toward the top toward the bottom into the screen out of the screen UNDETERMINED NONE

    7. A positive point charge is directly above a negative point charge.

    +

    -

    Both have the same absolute value and both are in the plane of the screen.
    What direction is their electric dipole moment?
    left right toward the top toward the bottom into the screen out of the screen UNDETERMINED NONE

    8. An electric dipole is in a uniform external electric field.
    The direction of its electric dipole moment is 25° N of E.
    The direction of the external electric field is opposite (25° S of W).
    What is the angle phi used to calculate torque and electric potential energy?
    zero 25° 90° 180°

    9. In Question 8 above, what direction should you choose for the electric potential energy?
    left right toward the top toward the bottom into the screen out of the screen UNDETERMINED NONE

    10. In Question 8 above, what direction should you choose for the torque?
    left right toward the top toward the bottom into the screen out of the screen UNDETERMINED NONE

    11. Another electric dipole is in another uniform external electric field.
    The direction of its electric dipole moment is into the screen.
    The direction of the external electric field is to the right.
    Now what is the angle phi used to calculate torque and electric potential energy?
    zero 90° 180°

    12. In Question 11 above, what direction should you choose for the torque?
    left right toward the top toward the bottom into the screen out of the screen UNDETERMINED NONE

    Strongly recommended by PHYS 242 students to learn a right-hand rule:
    Try these movies first.
    If the movies don't run on your computer, use these animated GIFs.

    Counter reset to zero 8/16/16.