1 / 11

PHY138 – Waves, Lecture 5 Today’s overview

PHY138 – Waves, Lecture 5 Today’s overview. Standing Waves Harmonics Beats. Reading Assignment.

Download Presentation

PHY138 – Waves, Lecture 5 Today’s overview

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. PHY138 – Waves, Lecture 5Today’s overview • Standing Waves • Harmonics • Beats

  2. Reading Assignment • Please read the following from Serway and Jewett before class on Wednesday: Chapter 24, Sections 24.3, 24.7 and 24.9, and Context 7, pg. 896-897. Only the concepts of 24.3 are important, not the equations. • A Web-CT quiz is due Wednesday morning, which tests your basic familiarity with Chapter 24 and 25 assigned reading.

  3. Written Homework The assignment due on Monday, November 29 at 5:00 PM is now available online. It includes problems from Chapter 14 and one from Chapter 24.

  4. Some Announcements: • Calculator hint: “Exp” key stands for “times 10 to the power”. ie, to type 10-3, type 1 Exp (-) 3, not 10 Exp (-) 3. (the latter will be interpreted as 10×10-3=10-2 !) • Friday Tutorials Representative Assembly: this Friday, noon-1:00PM, MP713. • New medical technique to help stroke victims: ultrasound. Sound waves can dissolve brain blockages. (J.P. Polak, New England Journal of Medicine v.351 n.21, pg. 2154, Nov. 18 2004)

  5. Doppler Effect sign conventions • Serway and Jewett say “A positive value is used for motion of the observer or the source toward the other.” • Other texts say: “A positive value is used for motion to the right, where the source is located to the right of the observer.”

  6. Some results of superposition • 14.2: Two waves, same frequency, same direction, diffferent phase: Interference • 14.3-5: Two waves, same frequency, opposite direction: Standing Wave • 14.6 Two waves, same direction, slightly different frequency: Beats

  7. Harmonic frequencies Transverse standing wave on a string clamped at both ends: there are nodes in displacement at both ends. Standing sound wave in a tube open at both ends: there are nodes in pressure both ends.

  8. a Quiz 1 b • A string is clamped at both ends and plucked so creates a standing wave. Define upward motion to be positive velocities. When the string is in position b, the instantaneous velocity of points along the string • 1. is zero everywhere • 2. is positive everywhere • 3. is negative everywhere • 4. depends on location c

  9. a Quiz 2 b • A string is clamped at both ends and plucked so creates a standing wave. Define upward motion to be positive velocities. When the string is in position c, the instantaneous velocity of points along the string • 1. is zero everywhere • 2. is positive everywhere • 3. is negative everywhere • 4. depends on location c

  10. Harmonic frequencies Standing sound wave in a tube closed at one end: there is a node in pressure at the open end, and an anti-node at the closed end.

  11. Beat frequency • The beat frequency is the difference of the frequencies of the two waves that are being added:

More Related