What property allows light to bend when passing from one medium to another?

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

Answer: (B)

Light bends when it passes from one medium to another because it changes speed. Different materials carry light at different speeds, and when the wavefront hits the boundary at an angle, the part of the light ray entering the new medium changes speed while the other part stays momentarily, causing the direction to shift. This bending toward the normal occurs when entering a denser medium and away from the normal when entering a less dense one. Snell’s law, which relates the angles to the refractive indices of the two media, describes this precisely. This phenomenon is what you observe when a straw looks bent in a glass of water and is essential for how lenses form images. The other terms describe different ideas: reflection is light bouncing off surfaces, diffraction is bending around obstacles or through small openings due to wave interference, and absorption is light energy being taken up by the material rather than redirected.