(c) Explain what is meant by the frequency of a wave.
(d) The sound intensity level increases by 6 dB as a person approaches a loudspeaker. By what factor does the sound intensity increase?
(e) The pitch of a musical note depends on its frequency. On what does (i) the quality, (ii) the loudness, of a musical note depend?
(f) A young man listening to his iPod turns up the volume, increasing the sound intensity from to
4 106 W m2 8 106 W m2 .What is the increase in sound intensity level?
(h) Some mobile phones have ring tones that are inaudible to older adults yet can be heard by children. How is this possible?
‘SECTION B’
HALF QUESTION Typical of Question 12 in Leaving Cert. Exam
Q6 Answer all of the following parts (a), (b) and (c). (a) Describe an experiment to show that sound is a wave motion.
The speed of sound depends on the medium through which the sound is travelling. Explain how sound travels through a medium.
Describe an experiment to demonstrate that sound requires a medium to travel.
(b) Resonance occurs when a vibrating object causes vibrations in nearby objects which have the same natural frequency.
Explain the underlined terms.
Describe an experiment to demonstrate resonance. Give an example of resonance. (4)
(c) The diagram shows a guitar string stretched between supports 0.75 m apart.The string is vibrating at its first harmonic.The speed of sound in the string is 420 m s1.
What is the frequency of vibration of the string? (9)
What is the name given to the points on the string marked (i) X, (ii) Y? (6) Draw a diagram of the string when it vibrates at its third harmonic.
What is the frequency of the third harmonic? X 0.75 m Fig 11.22
(7) (6)
Y
Vibrating guitar string
(12) (12)
(12) (6) (10)
(7) (7) (7) (7)
(g) A tin whistle produces a note of 256 Hz. Calculate the wavelength of this note.The speed of sound in air is 340 m s1.
