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How does refraction change the direction of light at a boundary between air and glass?
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When light travels from air into glass, it undergoes refraction, which is the change in direction caused by a change in the speed of the light wave. Because glass has a higher refractive index than air, light slows down upon entering the glass.1234
According to Snellās law, this change in speed causes the light ray to bend toward the normalāan imaginary line perpendicular to the boundary surface. The degree of this bending depends on the specific refractive indices of the two media and the angle at which the light strikes the boundary. Conversely, if light were to travel from glass back into air, it would speed up and bend away from the normal.342