In reflectance photometry, what happens to the light after the filter absorbs part of it?

In reflectance photometry, what happens to the light after the filter absorbs part of it?

• A. The remaining light is reflected and passes through slits
• B. It is transmitted through the sample
• C. It is completely absorbed
• D. It is converted to heat

Answer: (A)

In reflectance photometry, the light that makes it past the filtering still carries information about the sample. Part of the incident light is absorbed by the filter, but the portion that remains is what interacts with the sample—primarily by reflection from the surface. The instrument then collects this reflected light and channels it through the optical path, including the measurement slits, toward the detector. So the useful signal comes from light that is reflected off the sample and then passes through the slits to be measured. (Note that some energy may be absorbed in the sample as heat, but that does not prevent the reflected portion from reaching the detector.)

In reflectance photometry, the light that makes it past the filtering still carries information about the sample. Part of the incident light is absorbed by the filter, but the portion that remains is what interacts with the sample—primarily by reflection from the surface. The instrument then collects this reflected light and channels it through the optical path, including the measurement slits, toward the detector. So the useful signal comes from light that is reflected off the sample and then passes through the slits to be measured. (Note that some energy may be absorbed in the sample as heat, but that does not prevent the reflected portion from reaching the detector.)