Refraction of Light

Abstract

In general, when light encounters the boundary between two media, a part of the light is reflected and part is transmitted into the second medium.

Glossary of Terms

astigmatism

An aberration in a lens or mirror that causes the image of a point to spread out into a line.

converging lens

Lens that is thicker in the center; it causes parallel rays to converge and cross at the focus.

critical angle

The maximum angle of incidence for which a ray will pass from a slow medium (such as glass) to a faster medium (such as air); the minimum angle of incidence for which total internal reflection will occur.

diverging lens

Lens that is thinner at the center; it causes parallel rays to diverge and appear as if they came from the focus.

focal length

Distance from a lens (mirror) to the focus.

focus (focal point)

A point at which rays parallel to the axis of a lens will cross.

hyperopic

Farsighted , The eye forms images of near objects beyond the retina.

image

Replica of an object formed by a concentration of rays from the object.

index of refraction

Ratio of the speed of light in air to the speed in the medium.

lens

An optical device that can form images by refracting light rays.

magnification

The ratio of the size of image to size of object.

microscope

An optical instrument that enlarges tiny objects to make them visible.

mirage

An optical effect that produces an image in an unusual place due to refraction. Typically, the image appears as if it had been reflected from a water surface.

myopic

Nearsighted. The eye forms images of distant objects in front of the retina.

optic axis

The imaginary horizontal line that passes through the geometrical center of a lens.

optical fiber

A tiny glass pipe from which total internal reflection prevents the escape of light.

plane of incidence

Plane that contains the incident ray and the normal to the surface.

real image

An image created by a concentration of rays that can be projected onto a screen.

refraction

Bending that occurs when rays pass between two media with different speeds of light.

retina

The light-sensitive screen in the eye on which images are formed.

rods and cones

Light-sensing elements on the retina.

Snell’s law

A mathematical relationship between the angle of incidence, the angle of refraction (transmission), and the index (indices) of refraction.

telescope

Optical device for viewing and enlarging distant objects.

total internal reflection

Total reflection of light when it is incident at a large angle on an interface between a slow material (such as glass) and a faster material (such as air).

virtual image

An image formed by light rays that do not converge at the location of the image. A virtual image cannot be projected onto a screen.