Question

A solution of quinine with a known concentration of 0.164 μg cm-3 gave a reading of 82.0 in a fluorescence spectrophotometer.

A sample of tonic water was diluted 1:200 and then gave a reading of 56.8 in the same spectrophotometer.

a. Calculate the concentration of quinine in the original tonic water

b. Calculate the % transmission, if the length of the tube was doubled.

c. Explain how your results would change if you double the light intensity.

so I got how to solve question a. But when I try question b, I can't get any number on calculator

can anyone explain this question please?

Answer 1

b. According to Beers law

A = CL where A is Absorbance, is molar absoption coefficient, C is the Concentration and L is the length of sample tube.

If we keep and C as constant

A L

and Absorbance is inversely proportional to Transmission. So,

T 1/L where L is the path length of sample and T is transmission.

Hence, If the length of tube doubled the % of transmission will half of the value of initial  % of transmission.  

C.