The intensity of gamma radiation from a given source is l. On passing through 36mm of lead, it is reduced to l/8. The thickness of lead which will reduce the intensity to l/2 will be:
A
18mm
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B
12mm
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C
6mm
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D
9mm
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Solution
The correct option is B12mm
Given : Intensity of the gamma radiation from the source Io=l
Intensity I=Ioe−μx where x is the thickness of lead
Now for x=36mm , intensity becomes I=l8
∴l8=le−μ×36 (loge1/8=−2.079)
⟹μ=0.0578
Now let the thickness of lead be x so that the intensity becomes I=l2