Science Buddies: "Ask an Expert"

In the experiment "Measuring Sugar Content of a Liquid with a Laser Pointer", it is described that to measure the refractive index of a sugar solution one has to rotate the prism until the laser beam is parallel to the "untouched" side (procedure step 13), when there is only water inside of the prism.

My question is: Is it necessary to rotate the prism when I put in new solutions into the prism or do I keep it at the same position where the angle of minimum deviation was when there was only water in the prism? From intuition, the angle of minimum deviation relies on the refractive index of the solution. But it might also be the case that the increase in the deviation when a new solution is put in is negligible, or maybe I might be thinking about it in the wrong way.

Tell me if there's anything that needs clarification.


Moderator note: You posted the same question on the math and computer science forum so I deleted that post. Please read the instructions for posting at Science Buddies. Thank you.

Hi Muggo,

I’m assuming that you working on the project described here:

https://www.sciencebuddies.org/science- ... #procedure

Each sugar solution you test will have a different refractive index. So you’d expect different angles of minimum deviation. And the path of the laser through the prism will be different. You’ll need to rotate the prism for each solution you test. My suggestion is to follow project procedure steps 13 – 22 for each measurement.

I hope this helps. Please post again if you have more questions.

A. Norman

Hi,

In the experiment "Measuring Sugar Content of a Liquid with a Laser Pointer", a prism was used for the refraction of different solutions.

My question: Why is it that we specifically used a prism (wedge-shaped object) to calculate the refractive index? Why not a rectangular block or a cylinder?

Many thanks for anyone who is able to answer this question or/and refer me to a resource where I can obtain the answer. (I have had no luck so far in my searching.)

Moderator notes: please post your questions as replies on the same topic. I have moved this to your previous topic. Please read the guidelines for posting in Science Buddies. This is my second note to you.

Hello Muggo,

Sorry for the delay in replying to your latest post.

You can use a rectangular block for measuring refractive index. The following link describes a procedure for making the measurement:

http://www.pstcc.edu/departments/natura ... m%2010.htm

The prism procedure and associated geometry may be a bit easier.

I hope this helps. Please post again if you have more questions.

A. Norman