$\"\"$

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(a)

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The equation of level of sound is $\"\"$ , where $\"\"$ is an intesity of $\"\"$ .

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The intensity is $\"\"$ .

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Substitute $\"\"$ and $\"\"$ in $\"\"$ .

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$\"\"$

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Power property of logarithm : $\"\"$ .

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$\"\"$

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$\"\"$

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Apply property of logarithm : $\"\"$ .

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$\"\"$

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$\"\"$ .

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$\"\"$

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(b)

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The intensity is $\"\"$ .

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Substitute $\"\"$ and $\"\"$ in $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$ .

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$\"\"$

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(c)

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The intensity is $\"\"$ .

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Substitute $\"\"$ and $\"\"$ in $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$ .

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$\"\"$

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(d)

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The intensity is $\"\"$ .

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Substitute $\"\"$ and $\"\"$ in $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$ .

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$\"\"$

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(a) $\"\"$ .

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(b) $\"\"$ .

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(c) $\"\"$ .

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(d) $\"\"$ .