Question

After two hours, one-sixteenth of the starting amount of a certain radioactive isotope remained undecayed. The half life of the isotope is

• A. 15 minutes
• B. 30 minutes
• C. 45 minutes
• D. 4 hour

Answer 1

The Correct Option is B

The correct option is (B): 30 minutes
\(N=N_{0}\left(\frac{1}{2}\right)^{n}\) 
or \(\frac{N_{0}}{16}=N_{0}\left(\frac{1}{2}\right)^{n}\) 
or \(n=4\) 
Halflife \(t_{1/2}=\frac{t}{n}=\frac{2}{4}=\frac{1}{2} h\)
T=0.5hour=30 minutes.