7.9 Light Refraction

LIGHT REFRACTION

  • Learning Intention:

    • Describe the refraction of light through a convex and concave lens.

    • Explain the difference between focus and virtual focus.

REFRACTION

  • Definition:

    • Refraction is the bending of light due to a change in speed as it travels from one medium to another of different density.

  • Effect:

    • Light refraction can cause objects to appear distorted.

REFRACTIVE INDEX

  • Also Known As:

    • Optical density (denoted as n).

  • Definition:

    • It measures the amount of bending that occurs as light passes from one medium to another.

  • Impact on Speed of Light:

    • A lower refractive index indicates that light will travel faster through that medium.

REFRACTION MECHANICS

  • Incident Ray:

    • This is the ray of incoming light that strikes the boundary between two media.

  • Refracted Ray:

    • The ray of light that bends as it enters a different medium due to a change in speed (either when speeding up or slowing down).

  • Angle of Refraction:

    • This is the angle between the refracted ray and the normal line at the boundary between two media.

REFRACTIVE INDEX EXAMPLES

  • Example:

    • Water has a higher optical density than air; therefore, the speed of light decreases as it enters water from air.

    • As a result, the refracted ray bends towards the normal line at the interface.

  • Characterization of Dense Materials:

    • Dense materials are characterized by possessing a higher refractive index.

    • When light moves from a denser medium to a less dense medium, it bends away from the normal line.

LENSES

  • Definition:

    • Lenses are curved pieces of transparent material that modify the path of light rays passing through them.

Convex Lenses

  • Characteristics:

    • Thicker in the center compared to the edges.

  • Function:

    • Convex lenses cause light rays to converge (or come together) at a single point known as the focal point.

    • Focal Point:

    • This is the point where the converging light rays meet.

    • Focal Length:

    • This is the distance between the center of the lens and the focal point.

Concave Lenses

  • Characteristics:

    • Thinner in the center than at the edges.

  • Function:

    • Concave lenses cause light rays to diverge (or spread out).

    • Virtual Focus:

    • This is the point where a virtual image appears to be located, created by the divergent rays of light.