How to Measure Sugar Content With a Laser Pointer

When rays of light passes from air into water they bends because the refractive index of air is different from the refractive index of water. In other words, the rays of light travel with a different speed in the air than they do in water. Snell’s law describes this phenomenon, providing a mathematical correlation between the light beam is the approach in relation to a perpendicular line, which runs through the water, the refractive indexes of both materials through which light travels, and the refractive angle at which light travels through water.

The higher the refractive index, the more the light bends. Sugar water is heavier than plain water, so sugar water has a higher refractive index than plain water. Here we will use physics refraction to measure the content of water.

Things you need

  • 5 object glass, 1-inch by 3-inch
  • Epoxy
  • Paper
  • Tape
  • Laser pointer
  • Electrical tape
  • Calculator with trigonometric functions
  • Tape measure
  • Pencil
  • Sugar
  • Water

Make a Hollow Prism from Microscope Slides

1. Use epoxy to glue along the edges of four object glass to make a rectangular Prism.

2. Place the Prism on the top of a fifth rectangular object glass, and glue the Prism to the slide, using epoxy.

3. Allow the epoxy to set overnight.

Measuring refractive index of Sugar Water

4. Setup for experiments. Deck a wall with paper to make selections. Setup of the laser pointer, so that its beam is perpendicular to the wall. Attach the laser pointer in place and check it periodically to ensure that its beam is consistently hitting the same place when they pass through the air.

5. The right laser beam perpendicular through the Prism when it is empty. When the Prism is empty, the beam cannot be redirected. Mark the spot where the laser beam hits on the wall. Put a piece of paper under the laser and mark the point where the beam into the Prism (the two patches together, should form a straight line).

6. Fill Prism with fluid. Term the laser beam through the fluid-filled Prism. The beam will hit the wall some distance from the original brand. Select beam. Measure the distance between the two spots, distance a. measure the distance from the Prism to the wall, the distance (B).

7. With the two distances that you measured in step 3, you can calculate the angle where the beam hit the wall-in other words, its refractive angle after passage through the Prism. Calculate this angle by finding the inverse tangent of (distance (A) divided by the distance (B)).

8. Using Snell’s law, together with the angle that you calculated in step 4, in order to determine refractive index your fluid. According to Snell’s law, the relative refractive indices of two materials, or n2/n1 (n2 = refractive index of the material, n1 = refractive index of the first material) is equal to the sine of the angle divided by the sine of the angle of refraction. You aim your laser pointer perpendicular to the Prism, so your approach is 90. You calculated your refractive angle in step 4. And finally, the refractive index of air (N1) are 1.0003.

9. Create 1 percent, 5 percent, 10 percent and 50 percent solutions of sugar. Repeat steps 3 through 5 to determine their retraction indexes. Graph the sugar concentration versus refractive angle. Compare your retraction indices for known concentrations for refractive index that you calculated in step 5. . Estimate the concentration of sugar to your unknown solution.