The intensity of gamma radiation from a given source is `1` On passing through `36 mm` of lead , it is reduced to `(1)/(8)` . The thickness of lead which will redace the intensity to `(1)/(2)` will be
A
`9 mm `
B
`6 mm `
C
`12mm`
D
`18 mm`
Text Solution
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The correct Answer is:
C
KEY CONCEPT : intensity `I = I_(0)e^(-mu d)` Applying logrithm on both sides , `- mu d = log ((I)/(I_(0)))` `- mu xx = log ((I//8)/(I))`……(i) `- mu xx d= log ((I//2)/(I))`……(ii) Dividing (i) by(ii) `(36)/(d) = (log((1)/(8)))/(log((1)/(2))) = ( 3 log((1)/(2)))/(log((1)/(2))) = 3 or d = (36)/(3) = 12 mm`
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