Question

The half-life of radioactive Radon is 3.8 days. The time at the end of which (1/20)^th of the Radon sample will remain undecayed is (given log₁₀ e = 0.4343) –

• A. 13.8 days
• B. 16.5 days
• C. 53 days
• D. 76 days

Answer 1

Answer: (B)

16.5 days

Answer 2

Use N = N₀e^–lt

so t = $\frac { 1 } { \lambda }$ log_e $\left( \frac { \mathrm { N } _ { 0 } } { \mathrm {~N} } \right)$