In: Chemistry
Chlorophyll is known to have its absorption maximum at 680 nm (red light) with the extinction coefficient of 105 L/mol*cm. Assume a plant with leaves about 0.6 mm thick with the chlorophyll concentration of 0.0005 mol/L. How much red light in [%] will pass through a typical leave? Select one: a. 0.1 b. 10 c. 0.01 d. 0.3 e. 1
The Beer-Lambert law is an empirical relationship in relating the absorption of light to the amount of chemical when light is traveling through the sample. The Beer´s law states that absorbance (A) is proportional to the concentration (C) of the light-absorbing chemicals in the sample according to the following
A = E . l . C
Where E = molar absorptivity (L/mol.cm), l = length of light path in a sample cell, and C = concentration of the chemical (mol/L)
Transmittance (T) is used, which is defined as the fraction of the original ligth that has passed through the sample.
Absorbance and transmittance are related by A = -log10T and T = 10-A
The extinction coefficient is equal to the molar absortivity of leaf = 105 L/mol*cm
The thick of leaf is equal to the length of light path in a sample cell = 0.6mm = 0.06cm
The clorophyll concentration is equal to the oncentration of the chemical = 0.0005 mol/L
Then, substituting the values in the Beer-Lambert law equation:
A = 105 L/mol*cm x 0.06cm x 0.0005 mol/L
A = 0.00315
If you want to know " How much red light in [%] will pass through a typical leave?" you need to calculate the value of transmittance, with the following equation:
T = 10-A = 10-0.00315 = 0.9928 which is equal in percentage %T = 99.28
Considering the answer choices (a, b, c, d, e) it seems that the question should be relates to How much red light in [%] will NOT pass through a typical leave?
It is recommended to check the correct data of the question