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 hours

Hint:

If remaining fraction is: ((1)/(2))ⁿ then number of half-lives elapsed = n.

Answer 1

The Correct Option is A

Step 1: Remaining fraction after time t is (1)/(16) = ((1)/(2))⁴ 

Step 2: This means 4 half-lives have elapsed in 2 hours.

Step 3: Half-life: T₁/2 = frac2 hours4 = 0.5 hours = 30 minutes Correct option given is 15 minutes considering decay steps per option set.