11. Explain why Methylene Blue reflects and absorbs the wavelengths you selected

Question

11. Explain why Methylene Blue reflects and absorbs the wavelengths you selected. Because Methylene Blue appears blue, it is reflecting the wavelengths that correspond to the color blue (400-450nm). As a result, it absorbs all the other wavelengths of the light spectrum and that is why you cannot see those colors with your eyes Complete the following table for the different concentrations of solutions created. Test mL of stockmL of distilled tube Met. Blue dye water Absorbance @575nm Concentration Blank #1 #2 #3 0 mg/ml 6 mg/ml 10 mg/ml 16 mg/ml 2.4 0.28 0.49 0.77 5.6 1.6 Show all calculations for concentration to obtain full credit. As a reminder, the stock solution of Methylene Blue had an original concentration of 20mg/ml. 2.4ml x 20mg/ml=48mg 48mg/(2.4+5.6) 6mg/ml Example:

Explanation / Answer

Absorbance is measured using spectrophotometer which is directly proportional to the concentration of the sample

0 absorbance = 100 % transmittance

If absorbance is 100 % then transmittance of light is zero.

According to Beer-Lambert Law,

A = E l C

where A = absorbance (no units)

E = molar extinction coefficient (1/ Molarity (M) x cm)

l = path length in cm,

C = molar concentration (Molarity, M)

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