Q11 / 199 · NTA Abhyas (NEET) 2020 · Physics · Nuclear Physics

A sample of the radioactive element has a mass of 10 g at an instant t=0. The approximate mass of this element in the sample after two mean lives is

  • Correct answer
    A
    1.35 g
     
  • B
    2.50 g
  • C
    3.70 g
  • D
    6.30 g

Solution

Let, t = 0, M0 = 10 g

t = 2 τ = 2 1 λ given

Then from, M⁡ = M⁡ 0 e⁡ - λ t = 1 0 e⁡ - λ 2 λ

= 1 0 1 e⁡ 2 = 1 · 3 5 g.

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

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