Sample Experiments
USB2000 Operating Instructions
24
Reflection Experiments
Reflection is the return of radiation by a surface, without a change in wavelength. Reflection can be:
•
Specular (the angle of incidence is equal to the angle of reflection)
•
Diffuse (the angle of incidence is not equal to the angle of reflection)
Every surface returns both specular and diffuse reflections. Some surfaces may return mostly specular reflection,
while others may return mostly diffuse reflection. Specular reflection increases proportionately with the amount of
gloss on a surface.
Reflection is expressed as a percentage (%R
λ
) relative to the reflection from a standard reference substance…
S
λ
- D
λ
%R
λ
=
R
λ
- D
λ
x 100%
…where
S
λ
is the sample intensity at wavelength
λ
,
D
λ
is the dark intensity at wavelength
λ
,
R
λ
is the reference
intensity at wavelength
λ
.
Figure 6-3: Typical reflection setup. A light source (far right) sends light via the input leg of a reflection probe onto a
sample (bottom center). A reflection probe holder holds the probe in either a 90 or 45-degree angle from the surface. The
output leg of the reflection probe carries light from the sample to the spectrometer (top center), which is connected to the
PC (far left).
Common reflection applications include measuring the properties of mirrors and coatings. Other applications
include measuring the visual properties of the color in paints, plastics, and food products.
Summary of Contents for USB2000
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