Quiz4practice2.pdfQuiz4practice1.pdfQuiz 4A TA Name (last) (first) |___|___|___ Rubric Codes: Student ID: ____________________first 3 letters last name I certify by my signature that I will abide by the code of academic conduct of the University of California. Signature ! y(x,t) = A sin(2"tT±2"x#+$) + yo; ! " =vwavef; ! T = 1f; ! "= d sin# ; ! fbeat= f1" f2; ! fcarrier=f1+ f22 1) Two guitar strings are fixed at both ends. One string is made of metal; the other is made of nylon. The metal string has length S1. The nylon string has length S2 (which is shorter than S1). However, both guitar strings, when plucked, make the exact same note (same frequency when vibrating at its fundamental frequency as shown to the right). Which string has the faster wave speed? (To receive credit, you must explain your answer.) 2) Two speakers are playing slightly different frequencies; therefore, we hear beats. If you could adjust one of the speakers (change its frequency), describe how the beats change as the two frequencies become closer. S1S2f1 = f2Quiz 3E Student ID: ______________ Name: ________________ , ___________________ |_____| Rubric Codes: last first DL Sect. # I certify that I will abide by the UC Davis Code of Academic Conduct. Signature: ______________________ ANSWERS WITHOUT WORK WILL RECEIVE NO CREDIT. MARK YOUR ANSWERS CLEARLY. ! y(x,t) = Asin(2"tT±2"x#+$) |f1-f2|=fbeat fcarrier=! f1+ f22 d sin θ ≈Δx node-node: L=nλn/2 antinode-node: L=(2n-1)λn/4 Speed of light: 3x108m/s 1) Below are two images. In the image on the left, a laser (λ=600nm) shines on two very narrow slits (d=10-6m). After passing through the slits, the light travels two meters onto a screen, and you see a pattern of light and dark spots as shown. You mark the location of each bright spot with a white dashed line. Next, you add a device to one slit, which modifies the wave in some manner. The light is projected onto the same screen. The image with the device is below right. Image without device: Image with device: a) Explain what the device must be doing to make the center dark. You do not need to tell me how the device physically manipulates the light, as long as you can tell me the effect of the manipulation. A correct answer without complete justification will receive minimal credit. b) Why is the overall pattern neither compressed nor stretched out? Explain in terms of pathlength difference. 2) You create a standing wave on a guitar string, exciting the lowest frequency vibration. The middle of the string vibrates more than any other spot. At certain times, it passes through equilibrium. Two physics 7C students argue about what is happening while the middle is at equilibrium (names modified for confidentiality). A: That spot is a node so it is always a spot of constructive interference, even at equilibrium. B: While at equilibrium, the displacement is 0; therefore it is a case of destructive interference. Decide if either student is correct. Resolve the argument by writing an explanation of (all) the error(s). Neither answer seems outrageously wrong, so make certain to address why one might make the erroneous claim(s), and why the claim(s) is/are