Critical Angle & Total Internal Reflection
Obj: Determine critical angle for substances using Snell's Law
Materials: laser, glass rod, semicircular prism

Methods   (data sheet in pdf format)
Part I  Refraction at Less than the Critical Angle
1.  Place the semicircular prism in position on the data sheet.  Rotate the entire data sheet such that the incident LASER ray passes from the prism into the air as shown.
2. Measure the angle of incidence from the normal of the ray inside the semicircular prism .
3. Accurately draw all angles and fully label.
4.  Apply Snell's Law to calculate the index of refraction of the semicircular prism.

Part II  Refraction at the Critical Angle
5.  Place the semicircular prism in position on the data sheet.  Rotate the entire data sheet until the refracted ray passes along the flat surface of the semicircular prism.
6.  Accurately draw all angles and fully label.
7.  Apply Snell's Law to calculate the index of refraction of the semicircular prism.

Part III  Total Internal Reflection
8.  Place the semicircular prism in position on the data sheet.  Rotate the entire data sheet such that the incident LASER ray passes from the prism into the air as shown.
9.  Draw, label, and measure the incident and reflected rays.

Questions
1.  Define the terms:  index of refraction        critical angle        Snell's Law      
2.  Suggest uses of internal reflection in industry and the medical profession.  

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