gus1996
Posts: 3
Joined: Fri Nov 23, 2012 5:35 pm

Hi, I am conducting this experiement of measuring sugar content with a a laser pointer. I have done all the steps that the website says and am using sciencebuddies.org equipment as well. I have measured all index of refraction for all liquids with %10, %20, and %30 sugar concentration as shown in the table. However, I am stuck in the step that asks me to use the index of refraction to measure the sugar content. I don't know how to get from the index of refraction to the percentage of sugar concentration of an unknown liquid. Please help me as I have been trying to figure this out for a very long time and my project is due in less than a week.
Thank you, I really appreciate your help
Gustavo

gus1996
Posts: 3
Joined: Fri Nov 23, 2012 5:35 pm

The project is due in two days, any suggestions can help. Thanks

wendellwiggins
Former Expert
Posts: 338
Joined: Sun Jul 10, 2011 5:48 pm
Occupation: retired physicist

Hello gus1996,

I just reviewed the project at http://www.sciencebuddies.org/science-fair-projects/project_ideas/Phys_p028.shtml#summary.

I think you are expected to "interpolate" the sugar content from the results of your experiments on known-concentration solutions. You can do this using a very common technique called "linear interpolation." What that means is that you assume the index of refraction varies linearly (along a straight line) between your measured values.

Here's an example. Suppose you measure n(10%) = 1.3479 and n(20%) = 1.3639. Then you measure the index of refraction of an unknown solution and get n(unknown) = 1.3575.

1.3575 is at 60% of the distance between 1.3479 and 1.3639. The concentration of the unknown solution is then 60% of the distance between 10% sugar and 20% sugar, or 16% sugar.

Hope this helps, WW

gus1996
Posts: 3
Joined: Fri Nov 23, 2012 5:35 pm

Thank you so much, I found a formula on excel that interpolated the values for me. You really helped!
Thanks

AstroPie
Posts: 17
Joined: Sun Oct 28, 2012 10:32 pm