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Unformatted text preview: 0001-1 Physics 1240 Oct 27, 2005 Midterm #2 Version 0001 Don't be too quick to look at these! If you just worked through the practice exam, and then go here right away to look for answers to "check yourself", you are missing out on the main point of this exercise! You won't have that luxury on Thursday. You need to think about how to check YOURSELF. Come up with alternative explanations. Convince yourself! Talk to someone first, before looking to see if you're "right or wrong". What if you're right for the wrong reasons? That could totally mess you up if the question were just slightly different. Think about it some more... YOU need to come up with explanations - it will not help you to know an answer if you don't understand why, because we never like to just repeat the same question. 1. Suppose there are two tones playing simultaneously from two stationary instruments. The first tone is a steady 440 Hz, yet you hear beats once every 2 sec. What can you conclude must be true about the second tone? A) The second tone must be either louder or softer, but we can't easily tell which. B) The second tone must be 0.5 Hz higher C) The second tone must be 0.5 Hz lower D) The second tone must be 2 Hz higher E) The second tone must be 0.5 Hz different, but could be higher or lower, we can't easily tell which. 2. You are listening to two speakers. The distance from you to one of the speakers is precisely half a wavelength longer than the distance to the other one. Assume the speakers are wired to produce sound in synch (in phase) with one another. What do you hear when the speakers play the same pure tone? A) A sound softer than the loudness of either speaker alone B) A sound that beats (that is, it gets louder and softer, louder and softer, with time) C) A sound louder than either speaker alone would produce D) A sound of distinctly different frequency than either speaker alone would produce. E) A sound the same loudness as either speaker alone 3. What is the frequency of the note which is three octaves above 100 Hz? A) 103 Hz B) 200 Hz C) 400 Hz D) 600 Hz E) 800 Hz 4. How will the sound of a wind instrument change if you alter your fingering on the holes in such a way that the tube gets shorter by a factor of 2? A) The pitch goes up by 1 octave B) The pitch goes up by 2 octave C) The pitch goes down by 1 octave D) The pitch goes down by 2 octaves E) The pitch stays the same, the amplitude (and therefore loudness) is primarily what changes. 5. My dog Sasha is barking, producing a sound of 75 dB. Her evil twin Rasha is barking louder still, producing a bark of 100 dB. 0001-2 What is the ratio of the intensity (in W/m 2 ) produced by Rasha, to the intensity produced by Sasha?...
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