Spring 2007 Midterm1

# Spring 2007 Midterm1 - Spring 2007 Physics 214 Midterm Exam...

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Spring 2007 Physics 214 Midterm Exam (26 questions) The grading button and a description of the scoring criteria are at the bottom of this page. Basic questions are marked by a single star *. More difficult questions are marked by two stars **. The most challenging questions are marked by three stars ***. True-false questions are worth 2 points each, three-choice multiple choice questions are worth 3 points each, five-choice multiple choice questions are worth 6 points each. The maximum possible score is 120. The exam period was 90 minutes; the average score was 91.4; the median score was 93. Click here to see the formula sheet that came with the exam. QUESTION 1* To the right is a list of some equations describing how some field y(x,t) that depends on position x and time t changes. Which one of them does NOT obey the superposition principle? (a) (b) (c) (d) (e) QUESTION 2* Two sound waves with a frequency of 600 Hz and intensities 1.0 W/m 2 and 3.0 W/m 2 arrive at a microphone. What is the minimum possible intensity at the microphone? (a) 0.536 W/m 2 (b) 0.821 W/m 2 (c) 1.000 W/m 2 (d) 1.414 W/m 2 (e) 4.000 W/m 2 QUESTION 3*** Two speakers separated by 2 m emit sound of equal intensity in phase with a wavelength of 1 m. A listener walks around the speakers in a circle of radius 10 m. How many minima does the listener observe as he/she walks around the full circle? Page 1 of 9 Spring 2007 Physics 214 Midterm Exam 3/5/2007 http://online.physics.uiuc.edu/cgi/courses/shell/phys214/spring07/prep2a.pl?practice/exam1/. ..

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(a) 0 (b) 2 (c) 4 (d) 8 (e) 16 QUESTION 4** If three waves of equal amplitude A 1 are superimposed so that the total is A 1 cos(kx - ω t) + A 1 cos(kx - ω t + π /4) + A 1 cos(kx - ω t + π /2) what is the amplitude A tot of the resulting wave? (a) A tot = 1.000 A 1 (b) A tot = 1.732 A 1 (c) A tot = 1.848 A 1 (d) A tot = 2.414 A 1 (e) A tot = 3.000 A 1 QUESTION 5* This and the following two questions should be considered together. The figure below (not to scale) shows a light wave from a monochromatic source of wavelength λ = 6.0 × 10 -7 m, which goes through two small openings separated by a distance d = 3.3 mm, and forms a pattern on the screen which is at a distance L = 3 m. What is the frequency of the light? (a) f = 6.0 × 10 12 Hz (b) f = 5.0 × 10 14 Hz (c) f = 4.0 × 10 15 Hz QUESTION 6* What is the separation between bright spots Δ y in the resulting interference pattern? (a) Δ y = 4.3 × 10 -1 m (b) Δ y = 8.4 × 10 -2 m Page 2 of 9 Spring 2007 Physics 214 Midterm Exam 3/5/2007 http://online.physics.uiuc.edu/cgi/courses/shell/phys214/spring07/prep2a.pl?practice/exam1/. ..
(c) Δ y = 6.2 × 10 -3 m (d) Δ y = 5.4 × 10 -4 m (e) Δ y = 2.1 × 10 -5 m QUESTION 7* If the spacing d between the openings is increased slightly, does the separation between bright spots

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## This note was uploaded on 09/15/2008 for the course PHYS 214 taught by Professor Debevec during the Spring '07 term at University of Illinois at Urbana–Champaign.

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Spring 2007 Midterm1 - Spring 2007 Physics 214 Midterm Exam...

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