A tube with two open ends is 1 m long. What is the wavelength of the fundamental

Question

A tube with two open ends is 1 m long. What is the wavelength of the fundamental vibration of
an air column in this tube?
a. 2 m
b. 1 m
c. 0.5 m
d. 1/3 m
e. 4 m

For a sound wave of frequency 440 Hz, what is the wavelength
(i) in air (propagation speed, v = 3.3 * 102
m/s)?
(ii) in water (propagation speed, v = 1.5 * 103
m/s)?

a. (i) and (ii) the wavelength is the same, 0.75 m.
b. (i) 1.45 m, (ii) 6.6 m
c. (i) 6.89 m, (ii) 1.52 m
d. (i) 1.33 m, (ii) 0.29 m
e. (i) 0.75 m, (ii) 3.41 m

A point source of sound waves emits a disturbance with a power of 50 W = 50 J/s into a
surrounding homogeneous medium. What is the intensity of the sound at a distance of 10 m from
the source?
a. 5 W/m2

b. 0.5 W/m2

c. 0.08 W/m2

d. 0.04 W/m2

e. 0.4 W/m2

You have an empty 20 oz. soda bottle and you blow air over the opening to excite a fundamental
standing wave. Now you slice off the bottom of the bottle (it

Explanation / Answer

Answer question

1) Lambda = L/2 = 1/2 = 0.5 m

2)
i) wavelength = v/f = (3.3*100)/440 = 0.75 m
ii) wavelength = v/f = (1.5*1000)/440 = 3.41 m

e. (i) 0.75 m, (ii) 3.41 m

3) I = P/A = (50)/(4*pi*r^2) = 50/(4*3.14*10^2) = d. 0.04 W/m2

4) a. is higher than that in the first case.

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