Light bends and bounces in fascinating ways. Reflection occurs when light hits a surface and changes direction. Refraction happens when light passes between materials, altering its speed and path. These phenomena shape how we see the world.

Understanding reflection and refraction unlocks the secrets of mirrors, lenses, and optical illusions. From fiber optics to rainbows, these principles explain countless everyday experiences and cutting-edge technologies that manipulate light's behavior.

Reflection

Principles of Reflection

• Law of reflection states angle of incidence equals angle of reflection
• Angle of incidence measures between incident ray and normal line to surface
• Angle of reflection measures between reflected ray and normal line to surface
• Incident ray, reflected ray, and normal line all lie in same plane
• Reflection occurs when light bounces off a surface, changing direction

Types of Reflection

• Specular reflection happens on smooth surfaces (mirrors)
• Reflected rays remain parallel in specular reflection
• Diffuse reflection occurs on rough surfaces (paper)
• Reflected rays scatter in different directions in diffuse reflection
• Most real-world surfaces produce combination of specular and diffuse reflection

Applications of Reflection

• Mirrors utilize specular reflection for clear images
• Retroreflectors use multiple reflections to return light to its source (road signs)
• Solar cookers concentrate sunlight using reflective surfaces
• Telescopes employ reflective surfaces to gather and focus light from distant objects
• Fiber optic cables use total internal reflection for data transmission

Refraction

Fundamentals of Refraction

• Refraction describes bending of light as it passes between media of different densities
• Occurs due to change in light's speed when entering new medium
• Snell's Law mathematically relates angles of incidence and refraction: $n_1 \sin \theta_1 = n_2 \sin \theta_2$
• Index of refraction (n) measures how much a material slows down light
• $n = \frac{c}{v}$ where c is speed of light in vacuum and v is speed in medium
• Higher index of refraction indicates greater light bending

Behavior of Light During Refraction

• Light bends towards normal when entering denser medium (air to water)
• Light bends away from normal when entering less dense medium (water to air)
• Apparent depth illusion results from refraction (objects appear closer in water)
• Dispersion occurs when white light separates into component colors (prisms)
• Rainbows form due to refraction and internal reflection of sunlight in water droplets

Total Internal Reflection

• Total internal reflection happens when light attempts to exit denser medium at large angle
• Critical angle represents minimum angle for total internal reflection
• Calculated using $\sin \theta_c = \frac{n_2}{n_1}$ where n1 > n2
• No light passes through interface beyond critical angle
• Fiber optics utilize total internal reflection for efficient light transmission
• Diamonds sparkle due to total internal reflection of light within the gem