Please answer all questions on page. Thank You! A microphone of surface area 2.0
ID: 1628367 • Letter: P
Question
Please answer all questions on page. Thank You!
A microphone of surface area 2.0 cm^2 absorbs 1.1 mW of sound. What is the intensity of sound hitting the microphone? A) 2.2 times 10^-5 W/m^2 B) 0.55 W/m^2 C) 2.2 W/m^2 D) 2.8 W/m^2 E) 5.5 W/m^2 The speed of sound in air is 340 m/s, and the density of air is 1.2 kg/m^3. If the displacement amplitude of a 440-Hz sound wave is 10 mu m, what is the intensity of the wave? A) 0.16 W/m^2 B) 0.32 W/m^2 C) 12 W/m^2 D) 16 W/m^2 E) 32 W/m^2 The sound level at a point P is 14 db below the sound level at a point 1.0 m from a point source. Assuming the intensity from a point source drops off like the inverse square of the distance, the distance from the source to point P is: A) 4.0 cm B) 20 m C) 2.0 m D) 5.0 m E) 25 m If l_0 = 10^-12 W/m^2, and I = 4.5 times 10^-8 W/m^2, what is log (I/I_0)? A) 4.5 times 10^4 B) 18 C) 11 D) 4.7 E) 3.7 If the speed of sound is 340 m/s a plane flying at 400 m/s has a Mach number of: A) 0.85 B) 1.2 C) 1.4 D) 1.7 E) 400Explanation / Answer
17
P = power = 1.1 mW = 1.1 x 10-3 Watt
A = area = 2 cm2 = 2 x 10-4 m2
intensity is given as
I = P/A = (1.1 x 10-3 )/(2 x 10-4)
I = 5.5 W/m2
20.
log(I/Io) = log((4.5 x 10-8)/10-12) = 4.7