2nd request: A bat can detect objects?

Question

as small as an insect that is approximately equal to one wavelength of the sound that the bat makes. If the bat emits a chirp at a frequency of 62.3 kHz, and the speed of sound in the air is 334 m/s, what is the smallest insect a bat can detect (ans in mm)???

Answer 1

62.3 kHz is, by definition, 62300 waves/sec. Take its reciprocal and multiply by the speed of sound and you get:

(1 sec./62300 waves) * (334m/1 sec.) = 334m/62300 waves

You want to convert to mm,

334m/62300 waves * 1000mm/1m = 5.36mm/wave

So, the wavelength of the sound in air is 5.36mm; since the detection threshhold is 1 wavelength, the answer is 5.36mm.


Interesting stuff:
Microbat calls range in frequency from 14,000 to 100,000 Hz, mostly beyond the range of the human ear (typical human hearing range is considered to be from 20Hz to 20,000 Hz). The emitted vocalizations form a relatively broad beam of sound that is used to probe the environment.
taken from: http://en.wikipedia.org/wiki/Animal_echolocation#Echolocating_Bats

Answer 2

wavelength = propagation velocity / frequency so
334/62300 = .00536 m or a bit over 5 mm.


Doug