Half Value Thickness (HVT or HVL) – that amount of absorber that if placed in the path of the beam reduce the intensity by half, IF MEASURED  FROM THE SAME DISTANCE FROM THE SOURCE.

Linear attenuation Coefficient Equation:

Linear attenuation coefficient - is the percent reduction in intensity per unit thickness of absorber

Linear attenuation coefficient = mu (m)

 

Equation for finding the Final Intensity:

I_f = (TF) I_i       which is Intensity final = (Transmission Factor) x Intensity initial 

 

Transmission Factor Equation :

Transmission Fraction – the fraction of the beam that penetrates the block

TF = 2^-n                     

Half Life (T ½) – the amount of time that is required to reduce the radioactivity to ½ of its present value

 

Decay Constant Equation:

Decay Constant – the percent reduction per unit of time

Decay Constant = lambda (l)

           

Equation for finding the Final Activity:

A_f= (AF) A_i        which is the Activity final = (Activity Factor) x Activity initial

 

Activity Factor Equation:

Activity Fraction (AF) – the fraction of the activity that is remaining after a given amount of time

AF= 2^-n