Q5 / 117 · NTA Abhyas (JEE Main) 2020 · Physics · Waves and Sound

A sound absorber attenuates the sound level by 20 dB. The intensity decreases by a factor of

  • Correct answer
    A
    100
  • B
    1000
  • C
    10000
  • D
    10

Solution

L 1 = 10  log  I 1 I 0  ;  L 2 = 10  log  I 2 I 0

∴    L 1 - L 2 = 10  log  I 1 I 0 - 10  log  I 2 I 0

or   Δ L = 10  log  I 1 I 2   or    20  dB  = 10  log  I 1 I 2

or   10 2 = I 1 I 2       or   I 2 = I 1 100 .

Hence, the correct answer is option: 'A'.

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