filter (optics)

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In optics, a device that absorbs some parts of the visible spectrum and transmits others. A beam of white light can be made into a beam of coloured light by placing a transparent colour filter in the path of the beam. For example, a green filter will absorb or block all colours of the spectrum except green, which it allows to pass through. A yellow filter absorbs only light at the blue and violet end of the spectrum, transmitting red, orange, green, and yellow light.

Blue stands for peace. The tassel is a symbol of the monarchy. Yellow represents mineral wealth. Red symbolizes battle. Effective date: 30 October 1967. >>