 # Refraction Basics

When scientists talk about refraction, they use a formula. "n = c / v" "c" is the speed of light in a vacuum, "v" is the speed of light in that substance and "n" is the index of refraction. According to the formula, the index of refraction is the relation between the speed of light in a vacuum and the speed of light in a substance. But what is refraction? When light moves from one substance to another it changes speed and direction. That change in direction is called refraction. Some indexes of refraction are diamond (2.419), glass (1.523), and water (1.33).

Let's make a jump here. Since our formula says n=c/v and we know that the value for c is a constant, we can figure out that light has different speeds when it is in different substances. It goes at full speed in a vacuum, and slower everywhere else. Using our examples, we can discover that light moves faster in water than it does in a diamond. Light moves at its fastest speeds when it is in a vacuum. Light moves at about 124,000,000 meters per second (less than half the speed in a vacuum) in a diamond compared to 299,792,458 meters per second in a vacuum.

Light is refracted only when it hits a boundary at an angle, so if light goes straight down into a substance it will continue to move straight down. You need to understand that the speed of light changes in different substances. If a light ray slows down when it hits a substance, it bends towards the normal. The normal is the line that is perpendicular to the surface of the substance. If a light ray speeds up when it hits a substance, it moves away from the normal.  Or search the sites for a specific topic. Optics and Algebra (NASAConnect Video) Physics4Kids: Lenses
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