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. |