Sound with frequency 1300 Hz leaves a room through a doorway with a width of 1.03 m. At what minimum angle relative to the centerline perpendicular to the doorway will someone outside the room hear no sound

Question

Physics

Hadassah Wu

8 July, 05:42

Sound with frequency 1300 Hz leaves a room through a doorway with a width of 1.03 m. At what minimum angle relative to the centerline perpendicular to the doorway will someone outside the room hear no sound

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Answers (1)

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Daniel · Answer 1

about 14.7°

Explanation:

The formula for the angle of the first minimum is ...

sin (θ) = λ/a

where θ is the angle relative to the door centerline, λ is the wavelength of the sound, and "a" is the width of the door.

The wavelength of the sound is the speed of sound divided by the frequency:

λ = (340 m/s) / (1300 Hz) ≈ 0.261538 m

Then the angle of interest is ...

θ = arcsin (0.261538/1.03) ≈ 14.7°

At an angle of about 14.7°, someone outside the room will hear no sound.