The intensity of sound gets reduced by 20% on passing through a slab. The reduction in intensity on passing…

The intensity of sound gets reduced by 20% on passing through a slab. The reduction in intensity on passing through two consecutive slabs is
  1. 40%
  2. 36%
  3. 30%
  4. 50%

Solution

$100 \xrightarrow{\text{First slab}} 80 \xrightarrow{\text{Second slab}} 80\% \text{ of } 80 = 64$ $\therefore$ Reduction in intensity on passing through two slabs $= 36\%$

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