[abcc]

calculation question
The transmittance of a solution is found to be 40%. What is the transmittance if the solution is diluted in half?

[Dolphinsiu]

http://en.wikipedia.org/wiki/Transmittance

You can find it from above website!

T% = I/Io x 100%

Assume half-diluted solution is passed through by twice as light intensity in original solution,

Then A = - log 2I/Io + log I/Io = log I/2I = log 1/2 = -log T+ logTo = log 40/T

so log 1/2 = log 40/T

T = 80%

[enahs]

Go back to your basic Beer-Lambert Law and other formulas relation to transmittance.

A = ? * b * c
and
A= -log (T) -> T= 10^-A

T = 10^{-(? * b * c)}

What will happen?

Note, that is T, not %T

[Dolphinsiu]

Sorry! I have made a wrong mistake!
The last line should be T% = 80%

[chiralic]

To Dolphinsiu:

Could you tell us where come from the mathematical expression
A = - log 2I/Io + log I/Io that you wrote?

If you check a plot %T vs Concentration and Plot Absorbance vs Concentration you'll see that the %T vs C is not linear.

Regards,

Chiralic

[ARGOS++]

Dear ALL,

Have most of you already forgotten what Mr A. Beer, Mr. J. H. Lambert, and
Mr. P. Bouguer have told everybody about Light and Matter, ~250 years ago?

The Beer-Lambert-Bouguer Law:
http://www.p-forster.com/english/themes/Spectroscopy/BASICS/Corrected Beer's Law.htm

Good Luck!
                   ARGOS⁺⁺

P.S.:  Hint: Half the concentration is "exactly" the same as half the pathlength (Why?).
                ( "Wiki" is by far NOT all times a/the best Solution! )