SOUND WAVES EXERCISE SOLUTION
TOTAL MARK = 47
INSTRUCTIONS:
1. ANSWER ALL QUESTIONS
2. USE PPT PRESENTATION ON SOUND WAVES
3. USE SOUND WAVES NOTES MODULE (PDF)
QUESTION 1
Define the following as regards to sound waves
(a) Compression [2]
The region of a longitudinal wave in which the density and pressure are
greater than normal.
(b) Rarefaction [2]
The region of a longitudinal wave in which the density and pressure are less
than normal.
(c) Longitudinal Wave [2]
Wave in which the wave energy travels in the same direction as the particles
within the wave vibrate.
(d) Pitch [2]
How high or low we perceive a sound to be, depending on the frequency of
the sound wave.
QUESTION 2
(a) What is the difference between a longitudinal and a transverse wave [2]
For transverse wave, the direction of vibration of particles in
perpendicular to wave propagation whereas for a longitudinal wave the
direction of vibration of particles is parallel to the wave propagation
(b) Define Wavelength of a sound (longitudinal) wave [2]
Distance between consecutive compressions or consecutive rarefactions
(c) Explain how sound is produced by a loudspeaker [3]
Vibrating diaphragm of the loudspeaker causes the air particles in air to be
alternately compressed and relaxed thereby producing sound.
QUESTION 3
(a) State the speed of sound in the following
(i) Concrete [1]
5000m/s
(ii) Pure Water [1]
1400m/s
(iii) Gases [1]
330m/s
(b) In which medium does sound travel the fastest? [2]
In a solid
(c) In a bell Jar experiment, after all the air has been removed, one can see the
vibration of the bell but cannot hear the sound, why? [2]
Because there are no air particles that vibrate to produce sound [no medium
for the transmission of sound and sound cannot travel in a vacuum]
QUESTION 4
(a) What is the frequency range for a normal human ear? [2]
20Hz to 20 000Hz
(b) What is Ultrasound and what is it mainly used for? [3]
Sound above 20 000Hz mainly use for measuring distance (sonar)
(c) What is an echo? [2]
A reflected sound wave
QUESTION 5
(a) State 3 uses of sound waves to humans [3]
For communication
For finding objects by echolocation
Warn us about things that are about to occur
(b) What is meant by Noise Pollution [2]
Unwanted or disturbing sound
(c) State 3 characteristics of Sound Waves [3]
Frequency determine the pitch
Speed of sound depends on medium
Speed depends on temperature
QUESTION 6
(a) A mischievous child shouts ‘Barcelona!’ at a nearby cliff and hears an echo
2.4 s later. How far away is the cliff? Take the speed of sound = 340 m/s.
[3]
The sound travels to and from the cliff, a total distance of 2D
speed = distance / time
Hence: distance = speed x time
= 340 m/s x 2.4 s
= 816 m
= 2D !
Therefore distance to the cliff = 408 m.
(b) A thunderclap is heard 20 seconds after a lightning flash. Calculate the
distance to the lightning flash. Take the speed of sound = 340 m/s [3]
speed = distance / time
Hence: distance = speed x time
= 340 m/s x 20 seconds
= 6 800 m
(c) Draw two wave form to show the difference between
(i) Quiet and Loud Sound [2]
quiet loud
(ii) Low Pitch and High Pitch [2]
low pitch high pitch
