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Light Definitions
Term | Definition |
---|---|
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 |