What is the bending of light called?

• A. Refraction
• B. Reflection
• C. Diffraction
• D. Dispersion

Answer: (A)

Light bends when it passes from one medium into another because its speed changes. This change in direction is called refraction. The amount of bending is described by Snell’s law, n1 sin(theta1) = n2 sin(theta2), with n1 and n2 as the refractive indices of the two media. If light moves from a medium with a higher refractive index to a lower one, it bends away from the normal; going the other way it bends toward the normal. A familiar example is a straw that looks bent in a glass of water. In fiber optics, refraction at the boundary between the core and cladding helps establish how light enters and propagates inside the fiber, and combined with total internal reflection keeps the light guided along the length. Diffraction, reflection, and dispersion describe different phenomena: reflection is light bouncing off a boundary, diffraction is bending around edges or through openings, and dispersion is wavelength-dependent speed causing color separation—none of these describe the basic change in direction at a boundary like refraction.