Smart Lighting: Instructional Summary
“Reflection and Refraction of Light”
This project demonstrates how light bends as a part of its wave-like nature. Students will be
able to explain reflection and understand refraction enough to know that light bends when it
travels into a different medium.
The materials you will need include:
Demonstration One:
 One stand up mirror
 Laser pointer
 White piece of paper (screen)
Demonstration Two:
 Cubic zirconia
 Laser pointer
Demonstration Three:
 Medium-large clear plastic or glass container
 Skim milk or milk powder
 Water
 Strong laser pointer
 Optional: White piece of paper
Demonstration Four and Five:
 Knox gelatin (clear jello)
 Knife (or circle and square cookie cutters)
 Strong laser pointer
Demonstration Six:
 Fiber optic cables  Laser pointer
Demonstration One:
This experiment demonstrates reflection. Set up the mirror and paper so that the reflective
side of the mirror faces the piece of paper. (Start with an opener question on how light
reflects?) Explain how light reflects using a diagram that shows how the angle of incidence is
equal to the angle of reflection, ∠𝜃𝑖 = ∠𝜃𝑟 . Demonstrate reflection by changing the angle of
incidence and showing how the angle of reflection changes as result.
Demonstration Two:
This experiment also shows reflection. Pass the cubic zirconia around and point out how the
surface is cut at various angles. Explain how this means that the boundaries are at different
angles to each other. Ask the audience to predict what will happen to the reflected rays.
Point the laser at the cubic zirconia show that a unique pattern appears on the ceiling. Finish
by explaining how the rays reflected at all different angles.
Demonstration Three:
Demonstration Four:
Introduce the idea of refraction, 𝑛1 sin 𝜃1 = 𝑛2 sin 𝜃2 . (Focus more on the change of angle
than the change of speed or wavelength.) Based on refraction, ask whether light will bend
(toward or away from the normal) when a laser is pointed at a square of gelatin. Shine laser
at the jello at an angle so that it is clearly visible that the laser light bends.
Demonstration Five:
Introduce the idea that at some angle, light won’t refract. Introduce the idea of total internal
reflection by explaining that in a circle the boundary angle is constantly changing. When a
light is pointed at a certain angle the light is never at an angle to the normal that it can
refract and will solely reflect. Show this by shining a laser at a circle of jello.
Demonstration Six:
This shows a real life application of total internal reflection. Pass around fiber optic cables.
Explain that each cable has a cross section like the circular jello and will trap the light in the
cable. Shine the laser through one end of the cable and display the other lighted side to the
audience. Separate audience into teams and distribute cables to teams. Teams will split in two
so that one half tries to send a code to the other half.
Filler: (Materials same as demonstration three)
This experiment demonstrates scattering. (Start with opener: “Why is the sky blue?”) Fill the
tank up to 5 inches with water. Mix one teaspoon of milk to the water. Shine light into tank.
If scattering does not occur, add milk until desired effect is achieved. Blue and yellow light
should be clearly visible. Explain how this shows why the sky appear blue (because blue light
scatters more than any other wavelength.)