Dogs can hear frequencies up to 45 kHz. What is the wavelength of a 45,000 Hz sound wave traveling through air at 0 degrees Celsius?
A2.0 x 10^7 m
B7.4 x 10^-3 m
C1.5 x 10^7 m
D1.4 x 10^2 m
Answer & Solution
Correct answer: B. 7.4 x 10^-3 m
1. Identify the knowns: f = 45,000 Hz and v = 331 m/s, the speed of sound in air at 0 degrees Celsius.
2. Use lambda = v / f.
3. Substitute the SI values: lambda = 331 m/s / 45,000 Hz = 7.36 x 10^-3 m, which rounds to 7.4 x 10^-3 m.
4. This matches option B.
5. Option A, 2.0 x 10^7 m, results from dividing frequency by speed instead of speed by frequency.
_Source: OpenStax Physics (CC BY 4.0), Ch 14 "Sound", section 14.1 Speed of Sound, Frequency, and Wavelength_
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