Q. The intensity of gamma radiation from a given source is $I_{o}$. On passing through 37.5 mm of lead it is reduced to $I_{o}/8.$ The thickness of lead which will reduce it to $I_{o}/2$ is
A) $(37.7)^{\frac{1}{3}}mm$
B) $(37.5)^{\frac{1}{4}}mm$
C) $37.5/3\ mm$
D) $(37.5/4)\ mm$
Explanation
(c) As $\frac{I}{I_{0}}e^{- \mu x}\therefore\frac{1}{8} = e^{- \mu}37.5$ …(i)
and $\frac{1}{2} = e^{- \mu x}$
Put in Eq. (i), $e^{- 3\mu x} = e^{- \mu}(37.5)$
$x = \frac{37.5}{3} = 12.5\ mm$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.