Question

Question 11 FULL SCREEN PRINTER VERSION BACK NET (a) A circular diaphragm 64 cm in diameter oscillates at a frequency of 28 kHz as an underwater source of sound used for submarine detection. Far from the source, the sound intensity is distributed as the diffraction pattern of a circular hole whose diameter equals that of the diaphragm. Take the speed of sound in water to be 1450 m/s and find the angle between the normal to the diaphragm and a line from the diaphragm to the first minimum. (b) Is there such a minimum for a source having an audible) frequency of 1.0 kHz? (a) Number Units the tolerance is +/-5%

Answer 1

5.665°

No

Diameter, d= 64 m - 0.64m frequency, f = 28KHZ speed of sound in water = 1450 mis (a) Rayleigh criterion sino = 1.22X o- smt (1.22x) = sm? ( 1.22 (/f)) = 0 = simt (1.22 X 1450 128x103 x 0.64 -> O- 5.665 (b) = 1000 Hz 122 V - 1.22 x 1450 - 2.7641 fd 1000 X 0.64 since 2.764 71 [simo cannot be greater than o No minimum INO