Question

The intensity of sound wave while passing through an elastic medium falls

down by 10% as it covers one metre distance through the medium. If the

initial intensity of the sound wave was 100 decibels, its value after it has

passed through 3 metre thickness of the medium will be

• A. 70 decibel
• B. 72.9 decibel
• C. 81 decibel
• D. 60 decibel

Answer 1

The correct option is B

72.9 decibel

After passing the 3 meter intensity is given by

$I_3=\frac{90}{100}\times \frac{90}{100}\times \frac{90}{100}\times I$ = 72.9 % of I

So the intensity is 72.9 decibel.