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

Answer: (B)

72.9 decibel

Answer 2

After passing the 3 meter intensity is given by

$I_{3} = \frac{90}{100} \times \frac{90}{100} \times \frac{90}{100} \times I = 72.9\%\mspace{6mu}\text{of }I$

So, the intensity is 72.9 decibel.