sound and waves

Section 1:

2008 Question 5 (c) What is the relationship between the frequency of a vibrating stretched string and its length?

2008 Question12 (b) The pitch of a musical note depends on its frequency. On what does (i) the quality, (ii) the loudness, of a musical note depend?

2007 No.12 (b) Define sound intensity. A loudspeaker has a power rating of 25 mW. What is the sound intensity at a distance of 3 m from the loudspeaker?

The loudspeaker is replaced by a speaker with a power rating of 50 mW. What is the change: (i) in the sound intensity? (ii) in the sound intensity level? The human ear is more sensitive to certain frequencies of sound.  How is this taken into account when measuring sound intensity levels?

Section 2.

2006 Question 3 A cylindrical column of air closed at one end and three different tuning forks were used in an experiment to measure the speed of sound in air. A tuning fork of frequency f was set vibrating and held over the column of air. The length of the column of air was adjusted until it was vibrating at its first harmonic and its length l was then measured. This procedure was repeated for each tuning fork. Finally, the diameter of the column of air was measured.  The following data was recorded.

f/Hz  512   480    426
l/cm  16.0  17.2  19.4

Diameter of column of air = 2.05 cm Describe
(i) how the length of the column of air was adjusted;
(ii) how the frequency of the column of air was measured;
(iii) how the diameter of the column of air was measured.
How was it known that the air column was vibrating at its first harmonic?
Using all of the data, calculate the speed of sound in air.

Section 3.
2006 Question 5 (d) A sound wave is diffracted as it passes through a doorway but a light wave is not. Explain why.

2006 Question 11 {first part} (a) How does resonance occur in an acoustic guitar?  (b) What is the relationship between frequency and tension for a stretched string?  (c) A stretched string of length 80 cm has a fundamental frequency of vibration of 400 Hz. What is the speed of the sound wave in the stretched string?

2005 Question 7 {middle part} Describe an experiment to demonstrate that sound is also a wave motion.  Sound travels as longitudinal waves while light travels as transverse waves.  Explain the difference between longitudinal and transverse waves.

2005 Question 12 (c) The frequency of a stretched string depends on its length.  Give two other factors that affect the frequency of a stretched string.

Draw a diagram of a string when it vibrates at its second harmonic.  What is the frequency of the second harmonic?

Section 4.

2004 Question 3 A student investigated the variation of the fundamental frequency f of a stretched string with its length l. Draw a labelled diagram of the apparatus used in this experiment.
Indicate on the diagram the points between which the length of the wire was measured.
The student drew a graph, as shown, using the data recorded in the experiment, to illustrate the relationship between the fundamental frequency of the string and its length.
State the relationship and explain how the graph verifies it.
The student then investigated the variation of the fundamental frequency f with tension T.
The length was kept constant throughout this investigation.
How was the tension measured? What relationship did the student discover?
Why was it necessary to keep the length constant?
How did the student know that the string was vibrating at its fundamental frequency?

Section 5.
2004 No.5 (d)  The sound intensity doubles as a person approaches a loudspeaker. What is the increase in the sound intensity level?

2003 Question 5 (e) Sound intensity level can be measured in dB or dB(A).  What is the difference between the two scales?

2003 Question 7  {first part} Describe an experiment to show that sound is a wave motion.
2002 Question 3 A student obtained the following data during an investigation of the variation of the fundamental frequency f of a stretched string with its tension T.  The length of the string was kept constant.
T/N    15     20       25       30      35      40       45
f /Hz 264    304    342      371   402    431     456

Describe, with the aid of a diagram, how the student obtained the data.  Why was the length of the string kept constant during the investigation?  Plot a suitable graph on graph paper to show the relationship between fundamental frequency and tension for the stretched string. From your graph, estimate the tension in the string when its fundamental frequency is 380 Hz.

2002 Question 5 (e) Define sound intensity.