Understanding Light and Vision
Light and Vision
Properties of Light
Light: An object capable of emitting light itself.
Opaque: A material that does not allow light to pass through.
Translucent: A material that allows some light to pass through.
Light Ray: A straight line representing the direction and propagation of light. It is a graphic representation with no thickness.
Light Beam: A physical representation of light. When light passes through a thin slit, it forms a beam, which has thickness.
Shadows: Formed when an object blocks light. Sharp shadows occur when the light source is small or distant. If the source is large and close, a shadow with a less defined edge is formed.
Electromagnetic Spectrum and Color
Electromagnetic Spectrum: The range of all types of electromagnetic radiation, including visible light. Substances can emit (emission spectrum) or absorb (absorption spectrum) this radiation.
Isaac Newton: Discovered that sunlight is composed of a spectrum of colors by passing it through a prism. This spectrum, called the chromatic spectrum, shows that white light is not the absence of color, but the sum of all colors.
Reflection and Mirrors
Wave Module: Used to describe certain light behaviors.
Mirror: Any surface that reflects light rays.
Incident Ray: The ray of light that strikes the mirror.
Reflected Ray: The ray of light that bounces off the mirror.
Laws of Reflection
- The incident ray, the reflected ray, and the normal (a line perpendicular to the mirror surface) are in the same plane.
- The angle of incidence (between the incident ray and the normal) equals the angle of reflection (between the reflected ray and the normal).
Mirror images are virtual (appear to be behind the mirror), upright (retain the same vertical orientation), and symmetrical (appear at the same distance from the mirror).
Angular Plane Mirrors: Formed by two flat mirrors at an angle. Placing an object between them creates multiple images, the number of which depends on the angle.
Refraction and the Eye
Refraction: The bending of light as it passes from one medium to another (e.g., air to water).
The Human Eye
The eye receives light rays and converts them into nerve impulses sent to the brain, where they are interpreted as images.
Arthropod Eyes: Found in insects and similar animals, these eyes have a different structure than human eyes.
The eye projects images onto the retina, which detects light and sends signals to the optic nerve.
The eye is filled with vitreous humor, a gel-like substance.
The lens focuses light onto the retina. The iris controls the amount of light entering the eye.
Refraction in the cornea allows us to focus light. This ability can decline with age.
The eye consists of eyelids, eyeballs (about 25mm in diameter), the lacrimal apparatus (tear ducts), and external ocular muscles, which enable 3D vision.
Iris: A network of fibers and blood vessels. Its color depends on the transparency of the fibers and the amount of pigment.
Blind Spot: The area where the optic nerve connects to the retina (optic papilla), which lacks sensory cells.
Pupil: The opening in the center of the iris that regulates light entering the eye.
Cornea: The transparent front part of the eye.
Crystalline Lens: A convex lens that focuses light. If opaque, it causes blurred vision.
Magnification
Magnifying Glass: A converging lens with a short focal length that creates an enlarged virtual image. It is used to view small objects in greater detail.