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Dye strength dims the light
Age 16 · Science
When light passes through a coloured solution, the dye absorbs part of it. The more concentrated the solution, the more light is absorbed, and a spectrophotometer measures this to find the concentration.
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In the picture
- Dilute solution: little dye, so little light absorbed
- Concentrated solution: much dye, so much light absorbed
- Light beam: gets weaker after each cuvette
- Detector: measures the light that gets through
Examples
- Checking how much dye is in a sports drink in a school lab
- Measuring the amount of haemoglobin in a blood sample
Key takeaways
- Absorbance rises in proportion to concentration (A = ε·l·c)
- Measuring absorbed light lets you work out an unknown concentration
Quiz: Dye strength dims the light (Age 16)
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A coloured solution is made twice as concentrated. What happens to the amount of light it absorbs?
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What can a spectrophotometer be used for?
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Light is shone through a dilute solution and through a concentrated solution of the same dye. Which one lets more light reach the detector?
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