Question

The decay constant of a radio isotope is λ. If A₁ and A₂ are its activities at times t₁ and t₂ respectively, the number of nuclei which have decayed during the time (t₁ - t₂)

(a) A₁t₁ - A₂t₂

(b) A₁ - A₂

(c) (A₁ - A₂)/ λ

(d) λ(A₁ - A₂)

Answer 1

The correct option is (c) (A₁ - A₂)/ λ.

Explanation:

A₁ = λ N₁ at time t₁ 

A₂ = λ N₂ at time t₂ 

Therefore. number of nuclei decayed during time interval (t₁ - t₂) is

N₁ - N₂ = (A₁ - A₂)/ λ