Reflection and refraction occur simultaneously when light strikes the boundary between two media having different refractive indices obliquely, meaning not perpendicularly. In this situation, a portion of the light is reflected back into the original medium, while the other portion is transmitted and refracted into the second medium. The angle of incidence (the angle at which the light strikes the surface) determines the relative amounts of reflection and refraction that occur. This phenomenon is fundamental in optics and is responsible for many of the effects we observe in the world around us, such as the bending of light as it passes from air to water or from glass to air.