The activity of a freshly prepared radioactive sample is 10¹⁰ disintegrations per second, whose mean life is 10⁹ s. The mass of an atom of this radio-isotope is 10⁻²⁵ kg. The mass (in mg) of the radioactive sample is?
2
4
1
3
Solution:
dN/dt = λN Therefore, N = 10¹⁰ atoms Mass of sample = 10⁻²⁵ * 10¹⁰ kg = 10⁻¹⁵ kg = 1 mg