6
The °Plato determination is made by measuring the refractive index of a
solution. Refractive Index is an optical characteristic of a substance and the
number of dissolved particles in it. Refractive Index is defined as the ratio of
the speed of light in empty space to the speed of light in the substance. A
result of this property is that light will “bend”, or change direction, when it
travels through a substance of different refractive index. This is called refraction.
When passing from a material with a higher to lower refractive index, there
is a critical angle at which an incoming beam of light can no longer refract,
but will instead be reflected off the interface. The critical angle can be used
to easily calculate the refractive index according to the equation:
sin (
θ
critical
) = n
2
/ n
1
Where n
2
is the refractive index of the lower‑density medium; n
1
is the refractive
index of the higher‑density medium.
In the
HI96841
, light from an LED passes through a prism in contact with
the sample. An image sensor determines the critical angle at which the light
is no longer refracted through the sample.
PRINCIPLE OF OPERA
TION
