Chapter 18, Problem 6ST

Interpretation Introduction

Interpretation:

The option that corresponds to the time that is required for the activity to drop to $\text{20 dpm}$ 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. The

half-life of a radioactive substance is defined as the time taken by half of its atoms to decay.