Question

SOUND WAVES

12. Observer 2 is three times as far from a point (spherical) source of sound as is observer 1.

The ratio I₂/I₁ of the intensities (observer 2 intensity to observer 1 intensity) of the sound detected by the observers is

a) 9

b) 1/9

c) 1/3

d) 3

13. Which of the following frequencies would correspond to a sound with an ultrasonic frequency?

a) 100Hz

b) 1000Hz

c) 10000Hz

d) 100000Hz

Answer 1

12 ans

Given that

Amplitude A1=A

amplitude A2=3A

now we find the intensity ratio I2/I1

I2/I1=A2^2/A1^2=3^2/1^2=9/1=9

so the correct option is A

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13 ans

basing on concept of the ultrasonic the frequency of sound produced in ultrasonic frequency is 1 Kz