Course:PHYS341/Archive/2016wTerm2/Assignments/A3

Reading Assignment 3 (Jan 23 for quiz on Jan 27)
Read sections 7.1-7.5, 8.1-8.3, 8.5-8.11 in the textbook. My questions will be non-numerical and I'll restrict my discussion of phase to "in-phase", "anti-phase", and "somewhere-in-between-phase".

Quiz 3 practice questions

1. Circle any correct statements.
A sound wave (pure tone) strikes a rigid wall in which there is a small circular aperture (diameter much smaller than the sound's wavelength):

(a) It will not get through.
(b) All the original wave will squeeze through the hole and proceed mostly in its original direction.
(c) All the original wave will squeeze through the hole and spread out in all available directions.
(d) The fraction of the original wave that strikes the hole will get through and proceed mostly in its original direction.
(e) The fraction of the original wave that strikes the hole will get through and spread out in all available directions.✓

2. Circle any correct statements.
A sound wave (pure tone) strikes a rigid wall in which there is a large aperture (diameter much larger than the sound's wavelength):

(a) It will not get through.
(b) All the original wave will squeeze through the hole and proceed mostly in its original direction.
(c) All the original wave will squeeze through the hole and spread out in all available directions.
(d) The fraction of the original wave incident on the hole will get through and proceed mostly in its original direction.✓
(e) The fraction of the original wave incident on the hole will get through and spread out in all available directions.

3. Circle any correct statements.
Two sound sources in a wide-open space play the same pure tone with equal amplitude; they are separated by about a wavelength (i.e. the separation is not small compared to the wavelength).

(a) Walking around these sound sources you will sometimes hear the pure tone and sometimes hardly anything at all.✓
(b) Walking around these sound sources you will always hear the tone at twice the volume of one of the sources alone.
(c) Walking around these sound sources you will sometimes hear double the single pure tone's frequency and sometimes hardly anything at all.
(d) Walking around these sound sources you will always hear double the single pure tone's frequency at the same volume.
(e) Walking around these sound sources you will sometimes hear double the single pure tone's frequency and sometimes hardly anything at all.

4. A harmonic oscillator (e.g. a thin, taught string or a uniform narrow tube of air) resonates at a set of frequencies that are in integer ratios (e.g. 1:2:3:4... or 1:3:5:7...). The sound radiated by a harmonic oscillator consists of a set of partials, which are pure tones, and their frequencies are in the same integer ratios. If the frequencies of the partials are not in integer ratios the partials are said to inharmonic . In all cases, musical timbre of the sound is determined by the relative amplitudes of the partials.

Use only the following words to fill in the blanks (some words may be used more than once):
amplitudes, frequencies, harmonic, inharmonic, phases, speeds, timbre

5. Sound sources that are much smaller than the wavelength of the sound they are producing tend to radiate sound equally in all directions. Sound sources that are much larger than the wavelength of the sound they are producing tend to radiate sound only in particular directions. In a concert hall we can hear a cellist playing high notes (whose wavelength is much smaller than the size of the cello) only because sound is reflected from and diffracted by all surfaces in the hall and will eventually reach our ears .

Use only the following words to fill in the blanks (some words may be used more than once):
amplitude, absorbed, diffracted, frequency, high, low, smaller, larger, reflected, wavelength