question_answer

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 [AIEEE 2005]

A) 6mm

B) 9mm

C) 18mm

D) 12mm

Correct Answer: D

Solution :

[d] The intensity is given by

where,  intensity of radiation

...(i)

Now, intensity is  and thickness is x', then

...(ii)

From Eqs. (i) and (ii), we get