Resource examines whether the speed of light is constant or changeable. Features abstracts of scholarly papers.

Peruse and download introductory physics textbooks that cover topics such as electricity, optics and waves. Also find astronomy software.

Offers measurement and calibration services in photometry, optics, EMC and radiometry. Sells lighting design software and luxmeter instruments.

Produces X-rays and imagery used in electron microscopes and televisions.

Brief encyclopedia article explains the propagation of polarized light waves through some crystals.

Defines diffraction as a modification of light and other waves and mentions some of its applications.

Encyclopedia entry explains how this device is used to measure the wavelengths of light beams.

Find out how relativity theory describes how stars and galaxies can bend light and produce double images of distant objects.

Find out how ice crystals can bend light around the sun or moon to create this interesting visual effect.

Learn about detecting longer-wavelength light waves not visible to the human eye. Covers astronomical and medical applications.

Learn of a method used to measure the size of wavelengths and the distance between objects.

Defines the physical and perceptual characteristics of this common form of energy.

Learn how distance is measured using the speed of light as a standard.

Learn about the generation of microwaves through stimulated emission.

Provides a scientific overview of the photoelectric cell, or electric eye, including its uses, synonyms and operating principles.

Defines and gives an overview of this term referring to the release of charged particles from matter interacting with electromagnetic radiation.

Learn about the uses, devices and research conducted using this process of measuring light intensity. Includes related links.

Describes the German physicist Max Planck's discovery of this fundamental constant, which provides a key underpinning of quantum theory.

Describes the purpose and the principles behind this tool for detecting infrared radiation and other forms of thermal energy.

Elucidates the workings of this physical principle, and discusses what is required to create a reflecting surface.

Identifies those wavelengths of light classified as UV and describes their effects on life, and the role ozone plays in blocking them.

Summarizes the characteristics and effects of this form of radiation, and discusses the history of scientific inquiry on the subject.

Article outlines University of Toronto professor John Moffat's theory that the speed of light may not be constant.

Find essays on thermalphysics covering such topics as Max Planck, Kirchhoff's law, the solar photosphere, and MAP and COBE satellites.