1) how is comparing the intensity of color of you\'re unknown to the intensity o

Question

1) how is comparing the intensity of color of you're unknown to the intensity of color of the stock solutions related to what the spectrophotometer does?
2) why are using a specific wavelength of light to record absorbance measurements for the dye ? 1) how is comparing the intensity of color of you're unknown to the intensity of color of the stock solutions related to what the spectrophotometer does?
2) why are using a specific wavelength of light to record absorbance measurements for the dye ?
2) why are using a specific wavelength of light to record absorbance measurements for the dye ?

Explanation / Answer

Part 1. Intensity of coloured solutions are generally measured with Spetrophotometer. Spectrophotometer measures the absorbed light by comparing the intensity of incident light to transmitted light.

We can compare intensity of color (unknown) and known intensity by relating intensities with Absorbance as per beer lambert law. This help us to relate concentration and intensities. Hence we can compre both solutions in terms of either concerntration or absorbance.

Generally intensity of light incident (known) is denoted by I0 and transmitted light is by It. If light of a particular wavelength in not absorbed, the intensity of the light directed at the solution (Io) would match the intensity of the beam transmitted by the solution (It). If some of the light is absorbed, the intensity of the beam transmitted through the solution will be less than that of the original intensity. The ratio of It and Io can be used to indicate the percentage of incoming light absorbed by the solution.

Percent transmittance. %T = It/Io x 100

Absorbance = -Log It/Io.

from these equation, we can measure unknown concentration of an analyte as per beer lambert law.

Part 2.

Absorbance measures what percentage of electromagnetic radiation absorbed. When colored solutions are irradiated with white light, they will selectively absorb light of some wavelengths. Because, Electrons in a molecule (or atoms) absorb energy of particular energy and get excited to higher energy level. When they move form higher energy level to lower level for stable energy level-a photon of light is emitted. It imparts color to solution. Then it can be measured as percentage transmittance using intensity of light incident and transmitted light in spectrophotometer. Since electronic structure is different for different atoms, requirement of energy and then wavelengths is also different.

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