Question

Half life of a substance is 20 minutes, then the
time between 33 % decay and 67 % decay will be
(a) 20 minutes (b) 40 minutes
(c) 50 minutes (d) 10 minutes

Answer 1

Answer:

A) 20 MINUTES

Explanation:

For 67% decay,

Remaining = 100% - 67% = 33% = 0.33

0.33 = 

⇒ ln(0.33) = -t1. ln(2) / 20

⇒t1 = -[ ln(0.33)×20÷ln(2) ]

⇒t1 = 31.99 min

Similarly

For 33% decay,

Remaining = 100% - 33% = 67% = 0.67

0.67 = 

⇒t2 = -[ ln(0.67)×20÷ln(2) ]

⇒t2 = 11.55 min

Difference = t1 - t2 = 20.44 minutes