The frequency separating audible waves and ultrasonic waves is considered to be

Question

The frequency separating audible waves and ultrasonic waves is considered to be 20 kHz. What wavelength in air at room temperature is associated with this frequency? (Assume the speed of sound to be 340 m/s.) a. 1.7 cm b. 5.2 cm c. 12 cm d. 34 cm e. 55 cm If I_0 = 10^-12 W/m^2 is the threshold of hearing, a sound with intensity I_1 = 10^-11 W/m^2 will give a certain decibel level. Suppose a new sound has an intensity I_2 = I_1^2/I_0. What is the new decibel level? a. 2.0 b. 10 c. 20 d. 100 e. it will square the decibel level

Explanation / Answer

9.

f = 20 kHz

v = 340 m/sec

lambda = v/f

lambda = 340/(20000) = 0.017 m

= 1.7 cm

correct option is A.

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