Anonymous asked in Science & MathematicsEngineering · 1 decade ago

What is an ultrasonic wave? / 53 kHz to 91 kHz Estimate the wavelengths in air of these frequencies.?

a) What is an ultrasonic wave?

b) The pipistrelle bat emits sound waves in the range 53 kHz to 91 kHz.

Estimate the wavelengths in air of these frequencies.

c) Why is a very short wavelength of benefit to bats?

many thanks for your help!!


2 Answers

  • 1 decade ago
    Best Answer

    Ananth got sound mixed up with light

    The velocity of sound in dry air at sea level is about 330m/s so the wavelength at 53kHz is 330 x 1000/53000 mm = 6.23 mm. You can get the value for 91kHz by using 91000 instead of 53000 in the denominator. It's obviously going to be around 4mm.

    The advantage of such high frequencies for the bat is that the associated wavelength is about the same or smaller than the insects it wants to catch and can therefore provide an echo from such insects. A long wavelength would not be scattered or reflected by such small objects.

    Humans with good hearing are able to detect sounds having a frequency up to about 20kHz. Sound waves with frequencies above that (i.e beyond human hearing perception) are classified as ultrasonic.

  • 1 decade ago



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