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Light Definitions

Light A form of energy that travels by electromagnetic waves
Reflection When light bounces off a surface
Diffuse Reflection When light is reflected off a surface that one would not normally regard as reflective
Regular Reflection When light is reflected off smooth surfaces such as a mirror
Object Location that the rays of light have come from prior to striking the mirror
Image Location from which the rays of light appear to be coming
Object Distance Distance between mirror and object
Image Distance Distance between mirror and image
Incident Ray The ray of light falling onto a mirror from an object or light source
Normal An imaginary line radiating perpendicularly from the mirror at the point where the incident ray strikes the mirror
Reflected Ray The ray of light bouncing off a mirror
Angle of Incidence Angle between the normal and the incident ray
Angle of Reflection Angle between the normal and the reflected ray
Parallax Relative movement of two objects due to the movement of the observer
Magnified Image When the image height is greater than the object height
Diminished Image When the image height is less than the object height
Inverted Image Image is upside down
Erect Image Image is same side up
Laterally Inverted Image When the right side of the object is on the left side of the image and vice versa
Real Image When light rays actually intersect
Virtual Image When light rays appear to intersect
Pole The centre point of a spherical mirror
Centre of Curvature Centre of the sphere from which a spherical mirror is made
Principal Axis of a Mirror Straight line joining pole to centre of curvature of a spherical mirror
Focus of a Mirror The point halfway between the centre of curvature and the pole of a spherical mirror
Focal Length of a Mirror Distance from focus to pole of a spherical mirror
Refraction of Light When light bends on passing from one medium to another
Refractive Index The ratio of sine I to sine r when light passes from a vacuum into a medium
Critical Angle The angle of incidence in the denser of two mediums which causes a refraction of 90°
Total Internal Reflection When light is reflected back from a boundary between two mediums; it occurs when the light is travelling from the dense into the less dense medium, striking the boundary with an angle of incidence greater than the critical angle
Optic Centre Centre point of a lens
Principal Axis of a Lens Straight line passing through the optic centre that enters the lens at right angles to the face of the lens
Principal Focus Point through which light travelling parallel to the principal axis converges to for a convex lens or appears to diverge for a concave lens
Focal Length of a Lens Distance from focus to the optic centre
Compound Lens Combination of two or more lenses in contact with each other
Accommodation Adjusting the focal length of a lens to focus near or distant objects clearly on the retina
Short-sightedness When distant objects cannot be seen clearly
Long-sightedness When near objects cannot be seen clearly
Spectrum Range of wavelengths present in the electromagnetic radiation
Dispersion The separating out of different wavelengths of light
Created by: conordesmond