Reflective surfaces (climate engineering) quality (in the form of smog) the effect causes. By reflecting sunlight, light-colored roofs minimize the temperature rise and reduce cooling energy use and smog formation. A study by LBNL showed that, if strategies to mitigate this effect, including cool roofs, were widely adopted, the Greater Toronto metropolitan area could save more than $11 million annually on energy costs. Reflective surfaces (climate engineering) Reflective surfaces can deliver high solar reflectance (the ability to reflect the visible, infrared and ultraviolet wavelengths of the sun, reducing heat transfer to the surface) and high thermal emittance (the ability to radiate absorbed, or non-reflected,
Photoelectric effect certain threshold frequency (typically visible light for alkali metals, near ultraviolet for other metals, and extreme ultraviolet for non-metals), the radiation is absorbed and electrons are emitted. Light, and especially ultra-violet light, discharges negatively electrified bodies with the production of rays of the same nature as cathode rays. Under certain circumstances it can directly ionize gases. The first of these phenomena was discovered by Hertz and Hallwachs in 1887. The second was announced first by Philipp Lenard in 1900. The ultra-violet light to produce these effects may be obtained from an arc lamp, or by burning magnesium, or by sparking