Objectives

1.  To determine the degree to which the inverse square law holds for given radiation.

2.  To determine the linear absorption coefficient for a given absorber.

Background Reading:

- First period: appendix on errors and uncertainties.

- Second period: appendix on graphing.

Introduction

Radiation from radioactive substances is found to consist of up to three different kinds of rays: alpha (a ), beta (b ) and gamma (g ) rays. The penetrating power of these rays varies widely among them and is found to be a way of distinguishing among them based on their absorption in matter. This can be quantified into a mathematical form based on the thickness and type of absorber and the type of radiation.

The intensity of emission from a radioactive substance is found to decrease inversely as the square of the distance from the source. This occurs provided the source is small compared to the distance and the radiation is not significantly absorbed over that distance.