- Concave: A Lens That is Thinner, in the Middle, Than at its Edges.
- Convex: A Lens That is Thicker, in the Middle, Than at its Edges.
- Cornea: A Transparent Membrane that Protects the Eye and Refracts Light.
- Diffuse Reflection: Light Reflects at Different Angles.
- Electro-Magnetic Spectrum: Many Types of Light Like Visible Light, Ultraviolet Light, X-Rays, Radio Waves, and Much More, That is Aranged Fom Long to Short Wavelength or From Low to High Frequency.
- Illuminated: Visible Objects That Are Not A Light Source.
- Interference: A Wave Interaction, That Occurs, When Two or More Waves, Overlap.
- Iris: The Colored Part of the Eye.
- Lens: A Curved, Transparent Object That Forms an Image By Refracting Light to, for example, focus an Image on the Retina.
- Luminous: Objects That Produce Visible Light.
- Opaque: Matter That Does Not Transmit Light.
- Optic Nerve: The Nerve that sends the Image to the Brain.
- Photosynthesis: Light Energy, For Example, the Sun's Energy, to Produce New Substances with Chemical Energy.
- Pupil: The Opening to the Inside of the Eye.
- Regular Reflection: Light Reflects at Same Angles.
- Retina: The Back Surface of the Eye.
- Shadow: A Dark Reflection Cast, When in the Light.
- Translucent: Matter That Transmits Light, But Also the Light Passes Through the Matter.
- Transparent: Matter, Through Which Light, is Easily Transmitted.
- Visible Spectrum: The Range of Colors- "Roy G. Biv," Means Red, Orange, Yellow, Green, Blue, Indigo, and Violet- It's in That Order.