MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY
Colorimeter. Electronic colorimeter tests the hue of a sample in a test tube (at left). The device passes filtered light through the sample and the results are read on a computer monitor. The colour composition of the sample is determined by how much of each colour of light is absorbed by the sample. This is because each pigment in the dye will tend to block light which is not the same colour as it. For example, green dye will block red light but allow green through.
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