Which statement about transmittance (%) is correct?

Which statement about transmittance (%) is correct?

• A. %T = (I / I0) × 100
• B. %T = Absorbance
• C. %T = log10(A)
• D. %T = 1 / A

Answer: (A)

Transmittance tells us what fraction of the incoming light actually passes through the sample. If I0 is the incident light and I is the transmitted light, the transmittance as a fraction is T = I/I0. Expressing this as a percentage, %T = (I/I0) × 100. This is the standard way to report how much light makes it through. Absorbance, on the other hand, is a logarithmic measure related to transmittance by A = -log10(T) (with T as a decimal, not a percentage). So %T and absorbance are connected but not the same quantity. That’s why %T is not equal to absorbance, nor is it equal to log10(A) or to 1/A. The correct pathway is T = I/I0 and %T = 100 × (I/I0).

Transmittance tells us what fraction of the incoming light actually passes through the sample. If I0 is the incident light and I is the transmitted light, the transmittance as a fraction is T = I/I0. Expressing this as a percentage, %T = (I/I0) × 100. This is the standard way to report how much light makes it through.

Absorbance, on the other hand, is a logarithmic measure related to transmittance by A = -log10(T) (with T as a decimal, not a percentage). So %T and absorbance are connected but not the same quantity. That’s why %T is not equal to absorbance, nor is it equal to log10(A) or to 1/A. The correct pathway is T = I/I0 and %T = 100 × (I/I0).