Refraction Labs

III. Exploration - Quantative:

  1. Do the same as you did in Qualitative E, or use the same lines.
  2. At each place that the 2 lines touch the prism draw a line perpendicular to the prism.
  3. Continue it inside the prism.
  4. Measure all four angles formed next to the perpendiculars.
    You should have
    a. angle in air, b. angle in glass at one edge and
    c. angle in glass, d. angle in air at the other edge of prism.

  5. What did you notice about the angles?

Results:

  1. If you want to discover for yourself the equation relating the angles, continue here.
  2. If you want to take a shortcut, go to "Equations" below.
    1. Collect many pairs of angles in glass and angles in air, either by repeating many times or collaborating with your neighbors.
    2. Graph angle-in-air on the vertical axis and angle-in-glass on horizontal.
    3. Is it a straight line?
    4. (It should not be straight, if you graphed large enough angles.)
    5. Here is the part where you use your prior math knowledge: What function of angles is almost equal to the angle for small angles, but not as they get larger???
    6. If you think that you know, regraph using that function of each set of angles.
    7. Is it a straight line? If so, then you can write the relationship.

Equations:

Snell's Law:
n1 * sin q1 = n2 * sin q2.
n = "index of refraction" for a particular material. It tells how much that material bends the path of light.
By definition, n = 1.0 for vacuum. (It's OK to use that for air in most cases).

Light rays bend because light has different speeds in the two materials.


n1 * v1 = n2 * v2

8. Use "Snell's Law" and find the index of refraction for the glass you used.


Continue on to Refraction Explanations.
Index for Refraction.


Andria Erzberger
2/1/01