When using a a spectrophotometer to measure concentration changes in a colored solution you want to select the wavelength at which the greatest absorbance by the solution occurs.
Wavelength of light is related to energy by Planck's constant, h = 6.626 x 10^-34 J-s. The relationship is described by the equation E = h`nu` where = frequency or E = (hc)/`lambda` where c = speed of light (3.0 x 10^8 m/s) and `lambda` = wavelength.
When we...
When using a a spectrophotometer to measure concentration changes in a colored solution you want to select the wavelength at which the greatest absorbance by the solution occurs.
Wavelength of light is related to energy by Planck's constant, h = 6.626 x 10^-34 J-s. The relationship is described by the equation E = h`nu` where = frequency or E = (hc)/`lambda` where c = speed of light (3.0 x 10^8 m/s) and `lambda` = wavelength.
When we see a substance as a particular color, we're seeing the wavelengths or colors of light that it reflects. Other wavelengths are absorbed. The primary colors of light are red, green and blue. Secondary colors are yellow, magenta and blue-green.
When a primary color is absorbed, the remaining two primary colors that are reflected make up the complementary secondary color of the absorbed wavelength.
The purpose of the hint is to tell you that the range of maximum absorbance of the substance is most likely the complementary color of the color that the substance appears, not the color that you actually see in the spectrophotometer.
You can find the wavelength that has maximum absorption by starting at the shortest wavelength setting on the spectrophotometer and measuring the absorbance of your solution, then increasing the wavelength setting by 10 nm settings and repeating.
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