The half life of a radioactive substance is 20 minutes. The time taken between 50% decay and 87.5% decay of the substance will be

Options

A. 10 minutes
B. 25 minutes
C. 40 minutes
D. 30 minutes

Answer

C

Explanation

50% decay= 50% remaining
87.5% decay `rarr 12.5%` remaining
`therefore` time for 50% `rarr 25%` = 20min
time of `25% rarr 12.5 = ul("20 min")`
`ul("40 min")`