Index of Refraction
Name __________________
1.
Place your refraction tank onto the template labeled “Part 1”.
Be sure to center it over the outline.
2.
Turn on your ray box and align the ray with the line drawn on your template paper.
3.
Trace the ray that comes out of the refraction tank and label it “Air”
4.
Remove the refraction tank and use a pencil to draw a line from where the ray entered the
tank to where it came out of the tank.
5.
Repeat procedures 2 – 4, but this time, fill your tank with water. Trace the ray that
comes out of the tank and label it “water”.
6.
Repeat procedures 2 – 4, but this time, use your tank that is filled with corn syrup.
Trace the ray that comes out of the tank and label it “corn syrup”.
7.
Use a protractor to find the angle of incidence and the angles of refraction. Remember to
measure from the normal to the ray.
Angle of incidence: ____________
Angle of Refraction: (air) __________
6.
(water) __________
(corn syrup) __________
Use Snell’s Law to determine the index of refraction for water.
ni sin i  nr sin r
nair = 1.0008
nwater: __________________
7.
Use the equation n 
c
and the value for nwater obtained in procedure #6 to find the
v
velocity of light in water.
Velocity of light in water: ________________
8.
Use Snell’s Law to determine the index of refraction for syrup.
nsyrup: __________________
9.
Use the equation n 
c
and the value for nsyrup obtained in procedure #8 to find the
v
velocity of light in corn syrup.
Velocity of light in corn syrup: ________________
10.
Place your refraction tank filled with syrup onto the template labeled “Part 2”.
11.
Align the light ray with line “A” and trace its path all the way to the edge of the paper.
12.
Repeat procedure 11 for lines “B” and “C”.
13.
You should see a focal point where the lines converge. Mark this point on your paper
and label it “Focus”
14.
Flip the slotted plastic end piece over so that it makes three rays instead of one.
Align the center ray with line “B”. You should find that the beams cross at the focus.
14.
Remove your refraction tank and measure the distance from the middle of the tank to the focus.
This is the focal length.
Focal Length (syrup): _______________
15.
Compare the index of refraction of water to that of the syrup. Make a prediction about
how the focal length will differ when the tank is filled with water rather than syrup:
Prediction:
16.
Test your prediction: Replace the tank of syrup with a tank of water and measure the
focal length.
Focal Length (water): _______________
Questions
1.
Given that the index of refraction for diamond is 2.44, what would the angle of refraction
have been if you had used a diamond that was shaped like the refraction tank?
2.
Why are “ghost crystals” invisible in water, but visible in air?
3.
What is the invisible man’s index of refraction?
4.
Why does everything look blurry when you open your eyes underwater?