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Question: Radon (Ra) decays into Polonium (\(P_{0}\)) by emitting an \(\alpha -\)particle with half-life of 4 ...

Radon (Ra) decays into Polonium (P0P_{0}) by emitting an α\alpha -particle with half-life of 4 days. A sample contains 6.4×10106.4 \times 10^{10}atoms ofRnRn. After 12 days, the number of atoms of RnR_{n}left in the sample will be.

A

3.2×10103.2 \times 10^{10}

B

0.53×10100.53 \times 10^{10}

C

2.1×10102.1 \times 10^{10}

D

0.8×10100.8 \times 10^{10}

Answer

0.8×10100.8 \times 10^{10}

Explanation

Solution

In the given case, 12 days = 3 half lives Number of atoms left after 3 half lives.

=6.4×1010×123=0.8×1010= 6.4 \times 10^{10} \times \frac{1}{2^{3}} = 0.8 \times 10^{10}