How do electrochromic car mirrors work

It s quite common when driving at night to be dazzled by the lights of the vehicle behind as they reflect from the driver s new-view or door mirror. We can prevent the dazzle by forming a layer of coloured material over the reflecting surface within an electrochromic mirror. Such mirrors are sometimes called smart mirrors or electronic anti-dazzle mirrors . 

These mirrors are electrochromic if they contain a substance that changes colour according to its redox state. For example, methylene blue, MB+ (II), is a chromophore because it has an intense blue colour. II is a popular choice of electrochromic material for such mirrors it is blue when fully oxidized, but it becomes colourless when reduced according to 

Electrochromic mirrors are now a common feature in expensive cars. 

We discuss colour in Chapter 9, so we restrict ourselves here to saying the colour of a substance depends on the way its electrons interact with light crucially, absorption of a photon causes an electron to promote between the two frontier orbitals. The separation in energy between these two orbitals is E, the magnitude of which relates to the wavelength of the light absorbed X according to the Planck-Einstein equation, E = hc/X, where h is the Planck constant and c is the 

An electron is donated to an orbital during reduction. The electron removed during oxidation is taken from an orbital. 

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