In this lab, you will explore the behavior of light. You will observe reflection and refraction of a laser beam in jello, and use a diffraction pattern to measure the width of a hair.
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Student Version
Student Advanced Version
Recommended Prerequisites:
- Basic Lab: protractor use, basic calculator arithmetic
- Advanced Lab: protractor use, basic calculator arithmetic, basic trigonometry (sin and sin-1 with a calculator)
Key Concepts:
- Light always travels in a straight line except when it interacts with an object through reflection, refraction, or diffraction
- Reflection occurs when a light wave hits an obstacle (eg: a mirror) and bounces back (reflects).
- Some obstacles (eg: glass, water) allow light to pass through, but slow it down. In this case, the light ray bends as it crosses the object boundary. This is known as refraction. The angle of refraction depends on the speed of light in the object.
- Light waves can bend around a small obstacle or when passing through a narrow slit. Light waves generated by points around the obstacle overlap to create patterns of light and dark bands. This process is known as diffraction.
Materials:
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Red or yellow Jello mix (One 6 oz boxes per 8”x8” pan; two boxes per 9”x13” pan – each 8×8 pan provides materials for about 6 students/groups)
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Smooth (non-serrated!) knife
Every group of 2-3 students will need:
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1 laser pointer
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1 jello semicircle (about 2cm high, and 6cm diameter; exact dimensions do not matter)
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1 jello strip (about 2 cm by 2cm by 15 cm; length does not matter)
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1 protractor
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1 ruler or straight-edge
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1 meter stick
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Calculator (with a sine and inverse sine button, for advanced lab)
Ppencils, white paper, scissors
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Scotch tape
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OPTIONAL: a piece of horse-hair (eg: from a violin bow)