Two small stereo speakers A and B that are 1.40 m apart are sending out sound of
ID: 1496977 • Letter: T
Question
Two small stereo speakers A and B that are 1.40 m apart are sending out sound of wavelength 34.8 cm in all directions and all in phase. A person at point P starts out equidistant from both speakers and walks (see the figure (Figure 1) ) so that he is always 1.50 m from speaker B. Limit your solutions to the cases where x?1.50m.
Part A
For what values of x will the sound this person hears be maximally reinforced?
Enter you answers in decreasing order separating them with commas.
Part B
For what values of x will the sound this person hears be cancelled?
Enter you answers in decreasing order separating them with commas.
Explanation / Answer
given
wavelength of the sound, lamda = 34.8 cm = 0.348 m
A) for constructive intereference,
path difference = n*lamda (n = 0,1,2,3,4,5...)
1.5 - x = n*lamda
x = 1.5 - n*lamda
for n = 0,
x = 0
for n = 1,
x = 1.5 - 1*0.348 = 1.152 m
for n = 2,
x = 1.5 - 2*0.348 = 0.804 m
for n = 3,
x = 1.5 - 3*0.348 = 0.456 m
for n = 4,
x = 1.5 - 4*0.348 = 0.108 m
B)
for constructive intereference,
path difference = n*lamda/2 (n = 1,3,5,7...)
1.5 - x = n*lamda/2
x = 1.5 - n*lamda/2
for n = 0,
x = 0
for n = 1,
x = 1.5 - 1*0.348/2 = 1.326 m
for n = 3,
x = 1.5 - 3*0.348/2 = 0.978 m
for n = 5,
x = 1.5 - 5*0.348/2 = 0.63 m
for n = 7,
x = 1.5 - 7*0.348/2 = 0.282 m
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