Would the value of molar absorbitivity value be greater, less, or equal for the absorbance of light at 550nm vs 650 nm?
The molar absorptivity value, also known as the molar absorption coefficient, is a measure of how strongly a specific substance absorbs light at a particular wavelength. It is often denoted by the symbol ε (epsilon) and has units of L mol⁻¹ cm⁻¹.
To compare the molar absorptivity values at different wavelengths, we need to consider the Beer-Lambert Law. According to this law, the absorbance (A) of a solution is directly proportional to the concentration (c) of the absorbing species and the path length (b) of the light passing through the solution, and also to the molar absorptivity (ε) of the absorbing species at a specific wavelength.
Mathematically, the Beer-Lambert Law is expressed as:
A = εcb
Now, let's consider the absorbance of light at two different wavelengths, 550 nm and 650 nm. If we assume that the concentration and the path length are the same for both cases, we can cancel out those variables:
A₁ / A₂ = (ε₁cb) / (ε₂cb)
The concentration (c) and the path length (b) are the same for both wavelengths, so they cancel out. Therefore, the equation simplifies to:
A₁ / A₂ = ε₁ / ε₂
From this equation, we can see that the ratio of absorbance at these two wavelengths is equal to the ratio of their molar absorptivity values. If we assume that the concentration and path length remain constant, we can conclude that the molar absorptivity value is directly proportional to the absorbance.
Given this information, if the absorbance of light at 550 nm is greater than the absorbance at 650 nm (A₁ > A₂), then the molar absorptivity value at 550 nm (ε₁) would also be greater than the molar absorptivity value at 650 nm (ε₂). Conversely, if the absorbance at 650 nm is greater (A₂ > A₁), then the molar absorptivity value at 650 nm would be greater.
Therefore, without specific absorbance data, we cannot definitively say whether the molar absorptivity value would be greater, less, or equal for the absorbance of light at 550 nm versus 650 nm. To determine that, you would need to measure the absorbance of the substance at those wavelengths and compare the values.