Chapter 20, Problem 17E

Interpretation Introduction

Interpretation:

The number of half lives that have passed when radioactivity of a sample has dropped to $1/4$ of its original intensity is to be stated.

Concept introduction:

The elements whose nucleus decays spontaneously are known as radioactive elements. The decay is accompanied by the emission of alpha particles, beta particles, and gamma rays. All the elements which have an atomic number greater than $83$ are radioactive. Half-life of a radioactive substance is defined as the time taken by half of its atoms to decay.