REFRACTION summarized

Page 1: Refraction

  • Definition of Refraction: Refraction is the bending of light as it passes from one medium to another (e.g., air to water) due to changes in light speed.

  • Speed of Light:

    • In air: 3×10⁸ m/s

    • In water: 2.26×10⁸ m/s

  • Key Points about Refraction:

    • Light changes direction when entering a different medium.

    • Incident and refracted rays are on opposite sides of the boundary between media.

    • If entering a slower medium (air to water), light bends toward the normal line.

    • If entering a faster medium (water to air), light bends away from the normal.

  • Examples:

    • A straw appears broken or displaced in water due to the bending of light.

    • The curved spoon effect occurs when light travels from water to air, leading to a visual displacement of the spoon.

  • Important Note: A beam of light traveling perpendicular to a medium's surface will not be deflected but will still experience a change in speed.

Page 2: Refractive Index

  • Definition of Refractive Index: Light rays deviate between transparent media due to changes in speed, determined by the refractive indices of the media.

  • Refractive Index Equation:

    • n = c/v

      • n: refractive index

      • c: speed of light in a vacuum (3×10⁸ m/s)

      • v: speed of light in the medium

  • Characteristics:

    • Refractive index is a dimensionless quantity that shows how much the speed of light is slowed in a medium compared to air.

  • Example Calculation:

    • For glycerine with v = 2.04×10⁸ m/s:

      • n = 3.00×10⁸ m/s / 2.04×10⁸ m/s

      • n = 1.47

    • This indicates that light travels 1.47 times slower in glycerine than in air.

Page 3: Total Internal Reflection

  • Behavior of Light Between Media: A ray passing between media with the same refractive index changes direction, but returns on the same path if returning to the original medium.

  • Partial Reflection and Refraction: When light hits a reflective surface (water, glass), some rays reflect, and most refract.

  • Total Internal Reflection:

    • Occurs when light moves from a denser medium (e.g., acrylic) to a less dense one (e.g., air) and exceeds the critical angle.

    • Critical Angle: The angle at which the angle of refraction equals 90 degrees.

    • Conditions for Total Internal Reflection:

      1. The refractive index of the initial medium must be greater than that of the second medium (n1 > n2).

      2. The angle of incidence must exceed the critical angle.

    • Example: Water's critical angle is 48.8 degrees; angles greater than this cause total internal reflection.

Page 4: Optical Fiber

  • Definition and Function: Optical fibers transmit information using light through thin glass cables, utilizing total internal reflection to keep light contained within the fibers.

  • Applications:

    • Primarily used in telecommunications (high-speed internet, phones).

    • Employed in the medical field, such as in endoscopy.