The Law of Reflection states that when light reflects off the surface, the angle of incidence is equal to the angle of reflection. Snell’s Law states that when light crosses into a new medium, the relationship between the angle of incidence (θi) and angle of refraction (θr) are related by the equation:
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where n is the index of refraction.
There’s actually a connection between light reflection and refraction, since they usually happen at the same time.
Total internal reflection happens at large incident angles and when light travels from a more optically dense medium to a lesser dense medium. Total refers to no loss in intensity (plane mirrors have a loss of about 4%).
For total internal reflection to occur, two things have to happen: light must be going from more optically dense to less dense mediums, and the angle of incidence is greater than the critical angle.
Total internal reflection happens when light travels from water to air, not from air to water. It also happens when light bends away from the normal at large angles of incidence. For water-to-air, it’s greater than 48.6o. Each set of mediums have their own critical angle.
Click here to go to next lesson on Total Internal Reflection and Prisms
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