Optics is the branch of physics which involves the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultraviolet, and infrared light. Because light is an electromagnetic wave, other forms of electromagnetic radiation such as X-rays, microwaves, and radio waves exhibit similar properties.
Optoelectronics is the study and application of electronic devices and systems that source, detect and control light, usually considered a sub-field of photonics. In this context, light often includes invisible forms of radiation such as gamma rays, X-rays, ultraviolet and infrared, in addition to visible light. Optoelectronic devices are electrical-to-optical or optical-to-electrical transducers, or instruments that use such devices in their operation. Electro-optics is often erroneously used as a synonym, but is a wider branch of physics that concerns all interactions between light and electric fields, whether or not they form part of an electronic device.
Why has not man a microscopic eye? For this plain reason, Man is not a Fly. Say, what the use, were finer optics giv'n, T' inspect a mite, not comprehend the heav'n?
Alexander Pope, An Essay on Man (1733-34), Epistle I, line 193.
Harnessing the Sun's unlimited (for all practical purposes) energy supply is one of the most promising alternatives to combustion of fossil fuels. Improved characterisation of coatings for concentrating solar power (CSP) systems will speed development.