Chapter 15: Making Waves

Transcription

1 Chapter 15: Making Waves 1. Electromagnetic waves are generally A. transverse waves. B. longitudinal waves. C. a 50/50 combination of transverse and longitudinal waves. D. standing waves. 2. The period of a sound wave is the A. end of the wave. B. decade in which it is produced. C. inverse of its frequency. D. None of these. 3. The Doppler effect refers to changes in a sound wave s A. amplitude. B. duration. C. frequency. D. speed. 4. If the speed of sound is 1100 feet per second and a tuning fork oscillates at 440 cycles per second, what is the wavelength λ of the sound produced? A. 11 feet B. 4.4 feet C. 0.4 feet D. 2.5 feet 5. On a day when the speed of sound in air is 340 m/s, a lightning bolt is observed and the resultant thunderclap is heard 5 seconds afterwards. About how far away was the lightning bolt? A m B. 88,000 m C. 68 m D m 6. You hear a musician playing a series of notes of increasing frequency. As the frequency increases, the wave speed A. decreases. B. stays the same. C. increases.

2 7. Suppose an audible sound wave were being produced at a frequency of 800 cycles per second. If the frequency were doubled, the sound would become A. higher in pitch. B. louder. C. lower in pitch. D. softer. 8. Jim the meteorologist has predicted fair weather all day, but sees flashes of lightning followed by rolls of thunder. To calculate the distance to the lightning bolt, Jim should measure the time between the instant he first sees a lightning flash and the A. instant the lightning flash is over. B. instant he hears the beginning of the next thunder roll. C. instant he hears the middle of the next thunder roll. D. instant he hears the end of the next thunder roll. E. instant he sees the beginning of the next lightning flash. 9. As a wave passes from one medium into another, it often happens that its speed increases with no change in frequency. Under these circumstances, the wavelength A. decreases. B. stays the same. C. increases. 10. Two musical strings have the same length and tension, but string A has four times the mass of string B. The speed of a wave on string A is A. one fourth the speed of a wave on string B. B. one half the speed of a wave on string B. C. twice the speed of a wave on string B. D. four times the speed of a wave on string B. E. the same as the speed of a wave on string B. 11. The pitch of a sound is determined primarily by its A. frequency. B. duration. C. speed. D. amplitude.

3 12. To best excite the fundamental frequency of a guitar string, pluck it A. near one end. B. over the sound hole. C. with a pick. D. in the middle. 13. Which of these lists is in order of increasing wavelength? A. First harmonic, second harmonic, third harmonic. B. Second harmonic, third harmonic, fourth harmonic. C. First harmonic, second harmonic, fundamental. D. Third harmonic, second harmonic, first harmonic. 14. The principle of superposition tells us that, if two waves cross paths, A. the higher frequency wave will be on top. B. the net frequency is the sum of the individual wave frequencies. C. the net frequency is the sum of the individual wave speeds. D. the net displacement is the sum of the individual wave displacements. 15. A musical tone is coming from a loudspeaker. If a second loudspeaker nearby were to start playing exactly the same tone, the sound would A. get louder everywhere. B. get louder in some areas and stay the same in others. C. get louder in some areas and get softer in others. D. stay the same everywhere. 16. The tension in a guitar string is 21% too high. The fundamental frequency will be A. 21% too high. B. 10% too high. C. unchanged. D. too low. 17. When a wave reflects from a stationary boundary, A. the frequency decreases. B. the frequency is unchanged. C. the frequency increases.

4 18. When a wave crosses from one medium into another in which the wave speed is lower, the frequency is unchanged. The wavelength A. decreases. B. stays the same. C. increases. 19. Suppose an audible sound wave were being produced at a frequency of 800 cycles per second. If the amplitude were doubled, the sound would become A. louder. B. lower in pitch. C. higher in pitch. D. softer. 20. Which of the following is a longitudinal wave? A. a light wave B. a wave on string under tension C. a sound wave in a gas D. none of these E. all of these 21. Imagine you are holding a long rope under tension attached to a distant support. You can generate periodic waves by shaking the end up and down. Changing which of the following will least affect the velocity of waves along the string? A. frequency B. tension C. mass per unit length of rope 22. Suppose the velocity of waves on a particular rope under a tension of 10 N is 12 m/s. If the tension is increased fourfold to 40 N what will be the new velocity of waves on the rope? A. 48 m/s. B. 24 m/s. C. 18 m/s. D. 12 m/s. E. 6 m/s.

5 23. Waves on a particular string travel with a velocity of 20 m/s. A high-speed photograph shows that successive peaks are 0.80 m apart along the string. The frequency of the waves is: A. 25 Hz. B. 20 Hz. C. 16 Hz. D. 12 Hz. E. 8 Hz. 24. On a day when the speed of sound in air is 340 m/s, what will be the wavelength of sound of frequency 510 Hz? A. 510 m B. 3.0 m C. 1.5 m D m E m 25. Consider possible standing wave patterns for a string fastened at each end. Discussion in the text shows that there is a A. minimum possible wavelength. B. maximum possible frequency. C. maximum possible wavelength. D. maximum possible amplitude. 26. An organ pipe of length 3.0 m has one end closed. The two longest possible wavelengths for standing waves inside the pipe are A. 6 m and 3 m. B. 12 m and 6 m. C. 12 m and 4 m. D. 9 m and 6 m. E. 3 m and 1.5 m. 27. A string is held taut between two supports 2.0 m apart. The two longest possible wavelengths for standing waves are: A. 4 m and 2 m. B. 4 m and 3 m. C. 3 m and 1.5 m. D. 2 m and 1 m. E. 3 m and 2 m.

6 28. The speed of electromagnetic waves in air is 3.0 x 10 8 m/s. What is the wavelength of FM radio waves having a frequency of 1.0 x 10 8 Hz? A m B. 1.0 m C. 3.0 m D. 6.0 m E. 10 m 29. A fast train approaches a car waiting at a grade crossing and sounds its horn. A person in the car will notice that, compared to what it would be if the train were at rest, the A. wavelength appears to be longer. B. frequency appears to be higher. C. frequency appears to be lower. D. wavelength appears to be the same. 30. A harmonic wave has A. another wave nearby, so as to create harmony. B. a higher speed than a noise wave. C. to be a sound wave. D. a close correspondence to simple harmonic motion. 31. Captain Ahab notices that the waves passing the anchored Pequod are 20 feet from crest to crest, and that each minute 3 crests pass. The wave speed is A. 20 feet per minute. B. 40 feet per minute. C. 60 feet per minute. D. 80 feet per minute. 32. There is exactly one node present in the standing wave on a vibrating string. The frequency of oscillation of the string is the A. fundamental. B. first harmonic. C. second harmonic. D. third harmonic.

7 33. A standing wave is set up on a string so that it has 5 nodes. If you start at the central node and move exactly one wavelength in either direction, you will wind up at A. another node. B. an antinode. C. neither a node nor an antinode. D. Answer depends on the string mass per unit length. 34. End A of a Slinky is held motionless near the ceiling. End B is held on the floor so that there is a slight stretch. End B is quickly rotated one half turn about the axis of the Slinky and then returned to its original position, so as to twist and then untwist the coils. The wave so produced is a A. longitudinal wave. B. transverse wave. C. standing wave. D. none of these. 35. Points at which standing waves on a string have a maximum displacement are known as. Answer: antinodes 36. The number of cycles of a periodic wave passing a point in space per second is called the of the wave. Answer: frequency 37. The product of the frequency of a periodic wave times its wavelength gives the of the wave. Answer: speed 38. The distance between successive nodes for a standing wave pattern is wavelength. (Give multiple or fraction) Answer: 1/2 39. Increasing the air temperature inside an organ pipe, neglecting any expansion of the pipe, will the frequency of the fundamental tone. Answer: increase 40. Sound waves in water have a higher than sound waves in air. Answer: speed 41. Destructive interference is a result of two waves arriving at a point out of. Answer: phase, or step

8 42. Mechanical wave motion is a phenomenon in which there is a transport of without net motion of the medium. Answer: energy 43. Standing waves on a string produce a series of possible tones known as Answer: harmonics 44. An organ pipe open at one end will have a displacement node at the end. Answer: closed