2214F08Pre2v6solutions - Physics 2214, PRELIM II, November...

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Page 1 of 6 Physics 2214, PRELIM II, November 6, 2008 Brief solutions 1. [6 points] Recall the lecture demo where Dr. Giambattista whirled a tone generator fixed to a rod, around his head. Here's a diagram of that demo, viewed from above. You are sitting far away in the audience in the direction indicated. At which of the labeled point or points (A through H) do you hear the highest frequency sound? wavelength is shortened by approaching source 2. [6 points] A flute player is tuning her flute to a reference tone which plays at a frequency of 440 Hz. When she plays her note "A", she hears beats at a frequency of 3 Hz. She adjusts her flute (using the tuning slide) so that the length of the flute decreases. She notices that the beat frequency decreases. What was the fundamental frequency of the note that she was playing, before she adjusted the slide? If there is more than one possibility, list all of them. (A) 434 Hz (B) 437 Hz (C) 438.5 Hz (D) 440 Hz (E) 441.5 Hz (F) 443 Hz (F) 446 Hz from beat frequency, f = 443 Hz or 437 Hz. Decreased length increased f, which is closer to 440 Hz since the beat frequency decreases. 3. [6 points] In an ideal 1D standing sound wave, at what points is the potential energy density always zero? (A) at the displacement nodes (B) at the displacement antinodes because / sx = 0 (C) at certain points that are neither displacement nodes nor displacement antinodes (D) at no point G B B
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Page 2 of 6 B 4. [6 points] The nonzero field components for a traveling EM wave are 0 (,) c o s ( ) z Ex t E k x t ω =− and 0 c o s ( ) y B xt B kx t = −− . Which of the following is/are true about its Poynting vector?
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This note was uploaded on 12/24/2008 for the course PHYS 2214 taught by Professor Giambattista,a during the Fall '07 term at Cornell University (Engineering School).

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2214F08Pre2v6solutions - Physics 2214, PRELIM II, November...

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