Teledyne 460L User Manual

The detection of ozone molecules in a gas is based on the principle that ozone is a very strong 

absorber of UV light with a wavelength of 254 nm.  If the distance that this light travels through 
the gas is always the same, the more ozone present in a gas, the more UV light is absorbed.  If 

the distance the light travels through the gas, the intensity of light passing through the ozone 
containing gas, as well as the intensity of the light which does not pass through the gas are all 
known,  the amount of ozone present can be calculated according to the following equation, called 

Beer’s Law (also referred to as the Beer-Lambert equation). 

 



 

 

Where

:  

I

o 

is the intensity of the light if there was no absorption.  

  is the intensity with absorption.  

  is the absorption path, or the distance the light travels as it is being absorbed. This 

distance determines how many molecules are present in the column of gas in the 

absorption cell. 

  is the concentration of the absorbing gas. In the case of the Model 460L, Ozone (O

3

).  

  is the absorption coefficient absorption coefficient, a number that reflects the inherent 

ability of ozone to absorb 254 nm light.  Most current measurements place this value at 
308 cm-1 atm-1 at Standard Temperature and Pressure (STP).  The value of this 
number reflects the fact that ozone is a very efficient absorber of UV radiation which is 
why stratospheric ozone protects the life forms lower in the atmosphere from the 

harmful effects from solar UV radiation.