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prac3 - The Physics of Light& Sound PRACTICE PROBLEMS...

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Unformatted text preview: The Physics of Light & Sound PRACTICE PROBLEMS GENERAL SCIENCE 121 SUMMER 2011 1. A string fixed at both ends has a length of 4 m has a wave speed of 10 m/s. Compute the frequency of the 4th harmonic. ANSWER: 5 Hz 2. The fundamental frequency of a stretched string fixed at both ends is 238 Hz. If the length of the string doubled but the tension and mass per unit length did not change, what would be the new fundamental frequency? ANSWER: 119 Hz 3. A closed-open tube has a length of 3.9 m and a sound speed of 348 m/s. Compute the frequency of the 3rd harmonic. ANSWER: 67 Hz 4. An open-open tube has a length of 3.9 m and a sound speed of 345 m/s. Compute the frequency of the 5th harmonic. ANSWER 221 Hz 5. Notes of frequency ratio 2 to 3 so that harmonics of 2:3 or 4:6 etc. form is: A) a perfect fourthSean T Scully - GSCI121_3_4_SP10 B) a perfect fifth Homework #6 5 C) a minor third A 5 m cable ( mass/length of 0.0 ceiling. At the end of the cable, A standing wave is produced on a stretched string produce tension in the cable. W A standing wave is fixed at on a stretched as illustrated both ends as How produced both ends string fixed at below. illustrated below. aHow mental frequency of a standing wa many nodes and represent? many nodes and which harmonic does itwhich harmonic does it represent? D) an octave 6. Tries 0/10 Answer for Part: 0 ANSWER: 11 nodes 9 nodes and the 8th harmonic A. and the 10th harmonic B. 1 nodes that harmonics of 1:2 7. Notes of frequency ratio 11 to 2 soand the 10th harmonic or 2:4 etc. form is: A) a minor third C. 11 nodes and the 11th harmonic D. 9 nodes and the 9th harmonic B) a perfect fifth C) an octave Tries 0/10 Answer A flute (open-open) is played 362 hz. The length of the air the speed (in m/s!) of the wav Tries 0/10 Answer for Part: 0 • false • true 0 We wish to design an instrument • false that is constructed of an open-closed tube. The instrument • false needs to produce a note of 1280 hz frequency with the 5th harmonic. What would be the length D) a perfect fourth for Part: 8. of the tube (sound speed = 345 m/s)? ANSWER: 0.34 m Summer 2011 Notes of frequency ratio 3 to 4 so that harmonics of 3:4 or 6:8 etc. form is: A. a minor third B. a perfect fifth C. an octave 1 Practice Problems D. a perfect fourth Tries 0/10 • 4.6957427527 [4.46095561 4.930529890 Sig 0 - 15 • 564.72 [536.484 592.956] Sig 0 - 15 9. A 5 m cable ( mass/length of 0.04 kg/m) is hung from the ceiling. At the end of the cable, a 9 kg mass is attached to produce a tension in the cable. What would be the fundamental frequency of a standing wave produced in this cable? ANSWER: 4.7 Hz 10. A flute (open-open) is played with a first harmonic of 362 hz. The length of the air column is 78 cm. Find the speed of the wave resonating in the flute. ANSWER: 565 m/s 11. Sketch the first 5 harmonics for open-open, closed-open, and a Kundt tube. Label the nodes and antinodes. Determine the frequencies if the sound speed is 345 m/s and the length of each tube is 0.5 m. ANSWER: Kundt and open-open - 345, 690, 1035, 1380, and 1725 Hz (first second third fourth and fifth harmonics). Closed-open - 172.5, 517.5, 862.5, 1207.5, and 1552.5 Hz (first, third, fifth, seventh, and ninth harmonics). 12. Write down the electromagnetic spectrum in order of longest wavelength to shortest, highest frequency to lowest, lowest energy to highest ANSWER: Radio-IR-Optical-UV-X Ray-Gamma Ray Gamma Ray-X Ray-UV-OPtical-IR-Radio Radio-IR-Optical-UV-X Ray-Gamma Ray 13. Roemer first measured the speed of light by: A) Using an array of mirrors and a high powered light source B) Bouncing radio waves off of the Moon whose distance was known C) Spinning a gear while passing light through the cerated edge to a distant mirror D) Timing the difference in the period of Io (Jupiter's Moon) when the Earth was in two different locations in its orbit. 14. While looking through a telescope, you observe the Andromeda Galaxy which is 2.5 million light years away. Which of the following statements is correct? A) We are seeing Andromeda as it was two and a half million years ago B) There is not enough information to determine anything about "when" we see Andromeda C) We see Andromeda as it was 8 minutes ago D) We see Andromeda as it is today 15. Jupiter is 778,330,000 km from the Sun. How long (in hours) does it take light to travel from the Sun to Jupiter? ANSWER: 0.72 hours Summer 2011 2 Practice Problems ...
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