Question

Based on their half life, which of the following radioisotopes is most dangerous to handle?

• A. Half life of 3 billion years
• B. Half life of 100 years
• C. Half life of 0.01 minute
• D. Half life of 13 days

Hint:

Shorter half life means faster decay and higher activity, so it is more dangerous.

Answer 1

The Correct Option is C

Step 1: Recall the relation between half life and activity.
Activity, the rate of decay, is inversely related to half life. A short half life means the radioactive atoms are decaying very fast, releasing a large number of radioactive particles in a very short time. A long half life means the atoms decay slowly, releasing radiation gradually over a long period.

Step 2: Compare the given half lives.
A half life of 0.01 minute is extremely short, less than a second. This isotope decays almost instantly, releasing an intense burst of radiation in that short time, making it highly dangerous to handle at the moment of exposure.

Step 3: Compare with the others.
A half life of 3 billion years or 100 years means the isotope is decaying so slowly that only a tiny fraction of atoms decay in any short period, exposure over ordinary handling time gives a much lower radiation dose. A half life of 13 days is intermediate, it is more active than the very long lived isotopes but far less intense than the 0.01 minute isotope.

So option C, 0.01 minute, is the most dangerous because it has the highest activity per unit time.

Why the others are wrong: Options A and B have such long half lives that their activity is very low, they decay too slowly to cause acute exposure danger during normal handling. Option D is more active than A and B but still far less intense than option C.