chapter 14, sound, physics 220

SI Unit of time period is __________. 1. second 2. hour 3. minute 4. nanosecond

1

The frequency which is not audible to the human ear is 1. 50 Hz 2. 500 Hz 3. 5000 Hz 4. 50000 Hz

4

The speed of sound in air is about A 100 m/s B 300 m/s C 1000 m/s D 3 x 10 8 m/s

b

____ 6. The Doppler effect occurs with a. only sound waves. c. only water waves. b. only transverse waves. d. all waves.

d

____ 5. The distance between wave fronts of plane waves corresponds to ____ of a sound wave. a. one wavelength c. one compression b. two amplitudes d. two rarefactions

a

Q.14 A trumpet is playing at a level of 90 dB when the french horn joins in at 85 dB. Together they will generate a level of about A 90 dB B 91 dB C 93 dB D 175 dB

b

The 'pitch' of a musical note is normally given in terms of its A amplitude. B frequency. C wavelength. D speed.

b

We set up a loud speaker at the front of the room at ear level. the sound waves that pass thru' the room towards you will cause the air molecules in their path to A vibrate vertically up and down. B vibrate horizontally back and forward. C vibrate both vertically and horizontally. D move toward you in waves.

b

____ 13. The quality of a musical tone of a certain pitch results from a combination of a. fundamental frequencies. c. transverse waves. b. harmonics. d. velocities.

b

____ 14. How many beats per second are heard when two vibrating tuning forks having frequencies of 216 Hz and 224 Hz are held side by side? a. 6 Hz c. 9 Hz b. 8 Hz d. 3 Hz

b

____ 17. The frequency of a sound wave is 50 Hz. What is its period? a. 0.20 s d. 0.020 m/s b. 0.020 s e. 50 s c. 0.020 Hz

b

____ 19. When measuring the speed of sound outdoors, it is generally a. fastest in the spring d. fastest in the winter b. fastest in the summer e. the same for all seasons c. fastest in the autumn

b

____ 2. The shortest time interval in which a wave motion completely repeats itself (i.e., makes one complete vibration or oscillation) is called the a. amplitude d. frequency b. period e. speed c. wavelength

b

7. If you are on a train, how will the pitch of the train's whistle sound to you as the train moves? a. The pitch will become steadily higher. b. The pitch will become steadily lower. c. The pitch will not change. d. The pitch will become higher, then become lower.

c

Q.10 If the level of sound in the room is said to be 70 dB this means that the sound power intensity is A 7.0 x 10 -12 W/m5 B 1.0 x 10 -7 W/m5 C 1.0 x 10 -5 W/m5 D 70 x 10 -12 W/m5

c

Q.11 If the level of sound in the room increases to 76 dB (from 70 dB) the sound power intensity has gone up A only a fraction. B double C quadruple D six times

c

Sound is A a wave which travels through any material or a vacuum. B a wave which travels only through air. C a wave which travels through many materials but not a vacuum D particles which travel through most things.

c

____ 10. Which of the following decibel levels is nearest to the value that you would expect for a running vacuum cleaner? a. 10 dB c. 70 dB b. 30 dB d. 120 dB

c

____ 11. For a standing wave in an air column in a pipe that is open at both ends, there must be at least a. one node and one antinode. c. two antinodes and one node. b. two nodes and one antinode. d. two nodes and two antinodes.

c

____ 12. The wavelength of the fundamental frequency of a vibrating string of length L is a. 1/2 L. c. 2L. b. L. d. 4L.

c

____ 14. One sound source has an intensity of 40 dB, while another has an intensity of 70 dB. The intensity of these two differs by a factor of a. 3 d. 2800 b. 30 e. 1030 c. 1000

c

____ 16. Four beats per second are heard when two notes are sounded. The frequency of one note is 420 Hz. Which of the following is a possible frequency of the other note? a. 418 Hz c. 416 Hz b. 105 Hz d. 1680 Hz

c

____ 16. Which of the following intensities is 100 times greater than 10 dB? a. -90 dB d. 110 dB b. 0 dB e. 1000 dB c. 30 dB

c

____ 20. Scientifically, noise is best described as a. sounds that are unpleasant to humans b. the background hiss often heard on old recordings c. sound that originates from a source where the frequencies are not constant d. sound that originates from a source where only one frequency is produced e. the presence of three or more constant frequencies

c

When a wave travels through a medium ______. 1. particles are transferred from one place to another 2. energy is transferred in a periodic manner 3. energy is transferred at a constant speed 4. none of the above statements is applicable

2

Which of the following is not a characteristic of a musical sound? 1. Pitch 2. Wavelength 3. Quality 4. Loudness

2

An example for mechanical wave. 1. Radio wave 2. Light wave 3. Infrared radiation 4. Sound wave

4

Bats detect the obstacles in their path by receiving the reflected ______. 1. infrasonic waves 2. radio waves 3. electro-magnetic waves 4. ultrasonic waves

4

Sound waves do not travel through 1. solids 2. liquids 3. gases 4. vacuum

4

The frequency of a wave travelling at a speed of 500 ms-1 is 25 Hz. Its time period will be ______. 1. 20 s 2. 0.05 s 3. 25 s 4. 0.04 s

4

The speed of sound in medium depends upon 1. amplitude 2. frequency 3. wavelength 4. properties of the medium

4

Unit of wavelength is __________. 1. newton 2. erg 3. dyne 4. angstrom

4

Which of the following quantities is transferred during wave propagation? 1. Speed 2. Mass 3. Matter 4. Energy

4

____ 9. If the intensity of a sound is increased by a factor of 100, the new decibel level will increase a. by two units. c. by a factor of 10. b. to twice the old one. d. by 20 units.

d

A source of frequency of 500 Hz emits waves of wavelength 0.4 m, how long does the waves take to travel 600 m? 1. 3 s 2. 6 s 3. 9 s 4. 12 s

1

An ultrasonic wave is sent from a ship towards the bottom of the sea. It is found that the time interval between the sending and receiving of the wave is 1.6 s. What is the depth of the sea, if the velocity of sound in the seawater is 1400 m/s? 1. 1120 m 2. 560 m 3. 1400 m 4. 112 m

1

If a vibrator strikes the water 10 times in one second, then the frequency of wave is _________. 1. 10 Hz 2. 0.5 Hz 3. 5 Hz 4. 0.1 Hz

1

Sound waves are 1. longitudinal 2. transverse 3. partly longitudinal and partly transverse 4. sometimes longitudinal and sometimes transverse

1

The vibrations or the pressure variations inside the inner ear are converted into electrical signals by the_________. 1. cochlea 2. tympanic membrane 3. pinna 4. anvil

1

Vibrations inside the ear are amplified by the three bones namely the _________ in the middle ear. 1. hammer, anvil and stirrup 2. hammer, anvil and pinna 3. hammer, cochlea and stirrup 4. auditory bone, anvil and stirrup

1

When sound travels through air, the air particles ______. 1. vibrate along the direction of wave propagation 2. vibrate but not in any fixed direction 3. vibrate perpendicular to the direction of wave propagation 4. do not vibrate

1

The time period of a vibrating body is 0.05 s. The frequency of waves it emits is 1. 5 Hz 2. 20 Hz 3. 200 Hz 4. 2 Hz

2

A sound source sends waves of 400 Hz. It produces waves of wavelength 2.5 m. The velocity of sound waves is 1. 100 m/s 2. 1000 m/s 3. 10000 m/s 4. 3000 km/s

2

Sound and light waves both 1. have similar wavelength 2. obey the laws of reflection 3. travel as longitudinal waves 4. travel through vacuum

2

The method of detecting the presence, position and direction of motion of distant objects by reflecting a beam of sound waves is known as _____. 1. RADAR 2. SONAR 3. MIR 4. CRO

2

The minimum distance between the source and the reflector, so that an echo is heard is approximately equal to ______. 1. 10 m 2. 17 m 3. 34 m 4. 50 m

2

The relation between wave velocity 'v', frequency 'f ', and wavelength 'l' is ______. 1. f/λ 2. f*λ 3. λ/f 4. 1/f*λ

2

The amplitude of a wave is ______. 1. the distance the wave moves in one second 2. the distance the wave moves in one time period of the wave 3. the maximum distance moved by the medium particles on either side of the mean position 4. the distance equal to one wave length

3

The distance between a compression and the next rarefaction of a longitudinal wave is __________. 1. λ/4 2. 2l 3. λ/2 4. λ/8

3

The persistence of audible sound due to the successive reflections from the surrounding objects even after the source has stopped to produce that sound is called _________. 1. reflection 2. echo 3. reverberation 4. rarefaction

3

The physical quantity, which oscillates in most waves, is 1. mass 2. energy 3. amplitude 4. wavelength

3

The technique used by bats to find their way or to locate food is _______ 1. SONAR 2. RADAR 3. Echolocation 4. Flapping

3

Which of the following will remain unchanged when a sound wave travels in air or in water? 1. Amplitude 2. Wavelength 3. Frequency 4. Speed

3

____ 10. Which wave property most affects the intensity or loudness of sound? a. reflection d. amplitude b. complexity e. speed c. frequency

d

____ 18. During constructive interference in sound, which of the following could be produced? a. louder sound d. resonance b. node e. supercrest c. quieter sound

a

____ 15. A vibrating guitar string emits a tone just as a 5.00 × 10 Hz tuning fork is struck. If five beats per second are heard, which of the following is a possible frequency of vibration of the string? a. 2500 Hz c. 605 Hz b. 1500 Hz d. 495 Hz

d

____ 4. At a large distance from a sound source, spherical wave fronts are viewed as a. wavelengths. c. rays. b. troughs. d. plane waves.

d

____ 5. In a longitudinal wave, a. The particles move parallel to the direction of the wave motion. b. The particles move perpendicular to the direction of the wave motion. c. Energy causes the particles to move forward with the wave. d. Energy is propagated by crests and troughs. e. The speed is unaffected by the type of medium used.

a

2. Pitch depends on the ____ of a sound wave. a. frequency c. power b. amplitude d. speed

a

3. In general, sound travels faster through a. solids than through gases. c. gases than through liquids. b. gases than through solids. d. empty space than through matter.

a

Which of the alternatives (A to D) in the previous question indicates the loudness of the note?

a

____ 12. The change in direction of a sound wave around corners is called a. diffraction d. interference b. refraction e. resonance c. reflection

a

____ 15. Which of the following frequencies is infrasonic? a. 12 Hz d. 5000 Hz b. 25 Hz e. 25 000 Hz c. 332 Hz

a

____ 8. A water wave travels from shallow water to deep water and speeds up. Which of the following statements best describes the wave's behaviour as it changes mediums? a. The wavelength is shorter in the shallow water and longer in the deeper water. b. The wavelength is longer in the shallow water and shorter in the deeper water. c. The wavelength is unaffected. d. The frequency of the wave is lower in the shallow water and higher in the deeper water. e. The frequency of the wave is higher in the shallow water and lower in the deeper water.

a

____ 8. The property of sound called intensity is proportional to the rate at which energy flows through a. an area perpendicular to the direction of propagation. b. an area parallel to the direction of propagation. c. a cylindrical tube. d. a sound wave of a certain frequency.

a

____ 9. What will occur when the two pulses, shown below, interfere with each other? a. A node is created, then the pulses will continue to travel on unaffected. b. A super crest is created, then the pulses will continue to travel on unaffected. c. A node is created, then the pulses bounce off each other and return to their starting points. d. The two pulses completely destroy each other and they disappear. e. The two pulses join to form a new crest and travel to the left together

a

The speed of any periodic wave is given by Note: one or more of these may be correct. A the wavelength times the frequency. B the wavelength times the period. C the wavelength divided by the frequency. D the wavelength divided by the period.

a,d

Q.12 If the sound power intensity in the room doubles we will A hear a big difference in the loudness. B notice only a small difference. C not hear any difference at all. D be deafened.

b

1. The trough of the sine curve used to represent a sound wave corresponds to a. a compression. c. the amplitude. b. the wavelength. d. a rarefaction.

d

Q.13 The sound level at a rather noisy party (with disco) could be A 40 dB B 60 dB C 80 dB D 100 dB

d

Sound in air can best be described as a A transverse pressure wave of compressions and rarefactions in air. B transverse displacement wave which travels through air. C transverse polarised pressure wave in air. D longitudinal wave of air compressions and rarefactions.

d

____ 1. The speed of any mechanical wave as it propagates through a medium is dependent mainly on the a. frequency of the wave source b. wavelength c. period of the wave d. type of medium through which the wave travels e. amplitude

d

____ 11. Which of the following frequencies is ultrasonic? a. 12 Hz d. 5000 Hz b. 25 Hz e. 25 000 Hz c. 332 Hz

e

____ 13. An ambulance is approaching a stationary observer. For the observer, the apparent frequency of the siren compared to the actual frequency of the siren a. increases or decreases depending on the speed of the ambulance b. resonates c. decreases d. stays the same e. increases

e

____ 21. Waves that are produced on a guitar string by plucking it are a. sound waves d. acoustic waves b. longitudinal waves e. transverse waves c. electromagnetic waves

e

____ 3. A transverse wave has an amplitude of 2.4 m. What is the vertical distance, in metres, between the top of a crest and the bottom of a trough? a. 0.60 d. 3.6 b. 1.2 e. 4.8 c. 2.4

e

____ 4. Which point, shown in the diagram below, is in phase with point C? a. B d. F b. D e. G c. E

e

____ 6. In an ideal wave, which of the following wave properties does not change as it travels along the same medium? a. amplitude d. period b. wavelength e. all of the above c. frequency Name: ________________________ ID: A 2

e

____ 7. Consider the following wave properties: (i) speed (ii) frequency (iii) wavelength (iv) period Which of the above quantities does not change as a wave changes mediums? a. (i) only d. (i) and (iv) only b. (ii) only e. (ii) and (iv) only c. (i) and (iii) only

e