Index.of Showing(.jpg) Please Help Me Solve This Problem, I Have A Test Tomorrow On This. It's About The Refraction Of Light ?

Please help me solve this problem, I have a test tomorrow on this. It's about the refraction of light ? - index.of showing(.jpg)

We have had this experience where I connect to the light source in a standard, in conjunction with lens 12 and the square in front of him. Behind the lens, there was only a horizontal slit of the screen. We have glass on the slot screen, so that the beam through the glass. I need to win six measures, but I only managed that in this picture.

http://www.imagehosting.com/show.php/1670020_physics.JPG.html

This image represents the glass. The bottom screen is horizontal and the line is the jet. Can you tell me how to measure the refractive index of glass? How can I improve my career here? What parts has she? Measure Please help me, it's a disaster