Light and Optics

22A Light Behavior

• Luminous or Illuminated?

  • Luminous Object: an object that is producing visible light

  • Illuminated Object: an object that is visible because it reflects light from an external source

• Producing Light

  • Incandescence: the emission of light due to an object’s temperature

  • Fluorescence: the emission of light after an object absorbs high-energy electromagnetic waves

  • Phosphorescence: a slow emission of absorbed electromagnet energy, similar to fluorescence

  • Chemiluminescence: the emission of light energy from chemical reactions

• Ray: a model of light in which the endpoint represents the light’s source and the light travels in one direction

• Transparency

  • Transparent Material: a material through which light passes without scattering, transmitting a clear image

  • Translucent Material: a material through which light passes but the light is scatter and does not transmit a clear image

  • Opaque Material: a material through which visible light cannot pass

22B Color

• Additive Colors

  • Primary Colors: one of the three colors (red, blue, and green) of visible light that the human eye can sense; mixed to produce

  • Secondary Colors: a color of light that is produced when primary colors are mixed

  • Additive Color: a color that is produced by combining the wavelengths of different colors

• Subtractive Color: a color that forms because of pigments absorbing some wavelengths of light that strike an object

22C Reflection and Mirrors

• Reflection

  • Diffuse Reflection: the reflection off a rough or uneven surface that reflects light rays in all directions

  • Reflected Ray: the ray that bounces off a surface

  • Incident Ray: a light ray approaching a surface; an incoming ray

  • Law of Reflection: the law that states that when a light ray reflects off a surface, the angle of the incident ray equals the angle of the reflected ray

• Mirrors and Images

  • Plane Mirror: a flat mirror

  • Virtual Image: an image produced by diverging rays. The image is formed at the point from which the diverging rays would have originated. Because the rays don’t actually intersect, virtual images cannot be projected onto a screen

  • Real Image: an image that forms at the point where converging rays of light

  • Concave Mirror: a curved mirror with the reflective side on the inside of the curve

    • Focal Point: the point on an optical axel at which all reflected or refracted light rays from incident rays that are parallel to the optical axis converge

    • Focal Length: the distance from the center of a ens or mirror to its focal point

  • Convex Mirror: a curved mirror with the reflective side on the outside of the curve

22D Refraction and Lenses

Index of Refraction: the ratio of the speed of light in a vacuum to the speed if light in the medium

• Lenses

  • Lens: a disk of transparent material that refracts light to produce a real or virtual image

  • Converging Lens: a lens that causes light rays to come together (converge); also known as convex lens

  • Diverging Lens: a lens that causes light rays to separate (diverge); also known as concave lens