Light and Optics

Light is a form of electromagnetic radiation able to be detected by human eye. Human eye is sensitive to radiation only in a narrow range of wavelengths from about 400nm (violet) to about 700nm (red). The greatest sensitivity occurs near 555nm, corresponding to yellow-green color.

Theories of light include the obsolete corpuscular theory (Newton); the elastic solid ether theory (Fresnel) involving transverse waves; the electromagnetic theory (Maxwell), in which there are transverse oscillations of an electric field associated with similar transverse oscillations of a magnetic field at right angles to the electric field; the quantum theory (Einstein); in which the light is absorbed in packets of light quanta or photon.

Light is produced by surfaces at temperatures above about 900K to below about 6000K. Cold sources are certain chemical reactions, glowworms, lasers and discharge tubes. Cold sources are considered to be more efficient visible light sources.

A branch of physics concerned with the study of light, its production, propagation, measurement and properties is called optics. Geometrical optics is the use of ray diagram and the laws of reflection and refraction to determine the properties of lenses and mirrors. Physical optics is the study of the wave nature of light and includes such topics as diffraction, interference, polarization etc.

Traditional applications of optics include corrective lenses for vision and image formation by telescope and microscope. Modern applications include information storage and retrieval, such as in CD players or supermarket bar code scanners, and signal transmission through optical fiber cable.

Applets

Mirrors and raytracing

Lenses and raytracing

Thin lens combination

How a pinhole camera works?