Q74 / 90 · JEE Main 2021 (20 Jul Shift 2) · Physics

For a certain radioactive process, the graph between $\ln R$ and $t (\sec)$ is obtained as shown in the figure. Then the value of half life for the unknown radioactive material is approximately:

Solution

$R = R_{0} e^{- λ t}$

$ℓ n R = ℓ n R_{0} - λ t$

$- λ$ is slope of straight line

$λ = \frac{3}{20}$

$t_{1 / 2} = \frac{ℓ n 2}{λ} = 4.62$

Hence, the correct answer is option: 'D'.