Practice portal › Nuclei › Radioactivity

A sample of radioactive elements contains 4×10¹⁰ active nuclei. If half-life of element is 10 days, then the number of decayed nuclei after 30 days is

Asked in CBSE AIPMT 2002 · Decay law and half-life

Answer: (3) 3.5×10¹⁰

Step-by-step solution

Given: N₀=4×10¹⁰, T_1/2=10 days, t=30 days.

Number of half-lives: n=(30)/(10)=3.

Nuclei still undecayed: N=4×10¹⁰×(1/2)³=0.5×10¹⁰.

The question asks how many have decayed, which is the difference.

N₀-N=4×10¹⁰-0.5×10¹⁰=3.5×10¹⁰.

Why the other options are wrong

More Radioactivity questionsAll Radioactivity questions →

Reading this solution needs no sign-in. You only sign in to practise against the clock and keep your progress.

Practise this with a timer