Agilent Technologies Infinity 1260 - Page 12

12 Agilent 1260 Infinity RID User Manual
1 Introduction to the Refractive Index Detector
How the Detector Operates
According to the formula below small angles of external deflection are
proportional to the difference between the refractive indices of medium 1 and
medium 2.
Where:
• γ = angle of external deflection
• n
2
= Refractive index of medium 2
• n
1
= Refractive index of medium 1
Factors that Affect Refractive Index
The refractive index of a medium is affected by a number of factors;
1 Wavelength
The refractive index varies with changes in the wavelength of the incident
light beam.
2 Density
As the density of the medium changes the refractive index changes. At a
fixed wavelength of incident light the changes in refractive index are
generally linear in relation to the changes in medium density.
The density of a medium will be affected by the following factors:
• Composition (if not a pure substance)
• Temperature
• Pressure