Purpose: To demonstrate Snell's law and total internal reflection.

Turn on the power supply and adjust the light source to produce a narrow beam. Move the source to various angles of incidence, and verify Snell's law. When the light beam is incident from below the water surface, both the refracted and reflected beams are visible when the angle of incidence is less than the critical angle. As the angle increases toward the critical angle, it is clear that the amount of light in the refracted beam decreases to zero as the reflected beam increases to 100% of the incident. Measure the critical angle and compare with the value predicted from Snell's law.

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