The intensity of gamma radiation from a given source is `I`
On passing through `36 mm` of lead , it is reduced to `(1)/(8)` . The thickness of lead which will reduce the intensity to `(1)/(2)` will be

Options

A. `6 mm`
B. `9 mm`
C. `18 mm`
D. `12 mm`

Answer

D

Explanation

`l="le"^(-mux)`
`-mux=log.(l')/(l)`
`-mu.36=log.(1)/(8l)`.....(i)
`-mux'=log.(l)/(2l)`.....(ii)
From Eq.(i) and (ii),
`(36)/(x)=(3log((1)/(2)))/(log.(1)/(2))`
`:. x'12mm`