Optics Glossary Terms

Flashcards for Optics Glossary Terms

Incandescence

Light emitted from a material because of the very high temperature of the material.

Fluorescence

Light that is emitted during the exposure of the source to ultraviolet light.

Wavelength

The distance from one crest (or trough) of a wave to the next crest (or trough).

Reflection

The change in direction of a light ray when it bounces off a surface

Medium

The substance through which light travels

Ray

A straight line with an arrowhead that shows the direction in which light waves are travelling

Incident ray

A ray of light that travels from a light source toward a surface

Angle of Incidence

The angle between the incident ray and the normal in a ray diagram

Normal

A line that is perpendicular to a surface where a ray of light meets the surface

Reflected ray

A ray that begins at the point where the incident ray and normal meet

Angle of Reflection

The angle between the reflected ray and the normal in a ray diagram.

Plane mirror

A mirror with a flat, reflective surface

Virtual image

An image that is formed by rays that appear to be coming from a certain position, but are not actually coming from this position; image does not form a visible projection on screen.

Concave mirror

A mirror whose reflecting surface curves inwards

Principal axis

On a concave mirror, the line that passes through the centre of curvature, C, of the mirror and is normal to the centre of the mirror

Focal point

The point on the principle axis through which reflected rays pass when the incident rays are parallel to and near the principal axis.

Focal length

The distance between the vertex of a mirror and the focal point

Real image

An image that is formed when reflected rays meet

Magnification

The change in size of an optically produced image.

Spherical aberration (SA)

Irregularities in an image in a curved mirror that result when reflected rays from the outer parts of the mirror do not go through the focal point.

Convex mirror

A mirror whose reflecting surface curves outward.

Refraction

The bending of light as it travels, at an angle, from a material with one refractive index to a material with a different refractive index

Refracted ray

The ray that is bent upon entering a second medium

Angle of refraction

The angle between the normal and a refracted ray

Index of refraction

The ratio of the speed of light in a vacuum to the speed of light in a given medium

Partial reflection and refraction

A phenomenon in which some of the light that is travelling from one medium into another is reflected and some is refracted at the boundary between the media

Critical angle

The angle of incidence that produces an angle of refraction of 90 degrees, when light travels from a high to low index of refraction.

Total internal reflection

The phenomenon in which incident light is not refracted but is entirely reflected back from the boundary; occurs when light travels from a medium in which its speed is lower to a medium in which its speed is higher

Dispersion

The process of separating colours by refraction.

Lens

A transparent object with at least one curved side that causes light to refract

Converging lens

A lens that brings parallel light rays towards a common point

Diverging lens

A lens that spreads parallel light rays away from a common point.

Chromatic aberration

The dispersion of light through a lens

Objective lens

The lens through which light enters a telescope and a microscope

Eyepiece

The lens or mirror in a telescope through which the observer views the object and through which light leaves the telescope or microscope

Cornea

Tissue that forms a transparent, curved structure in the front of the eye; refracts light before it enters the eye

Retina

A layer of rod and cone cells that respond to light and initiate nerve impulses; rod cells are very sensitive to light but cannot distinguish between colours; cone cells detect colour

Myopia

near-sightedness; the condition in which the eye cannot focus on distant objects

Hyperopia

far-sightedness; the condition in which the eye cannot focus on nearby objects