COLOUR-TEMPERATURE
The measured peak level of the emission spectrum of unfiltered sunlight is located
around 500 nanometers, corresponding with the colour green. The reason why we
experience the colour of the sun as being yellowish can be found in filtering and
scattering by the earth's atmosphere but it is also caused by the relatively great
sensitivity of our eyes for yellow light. From Wien's displacement law it can be
calculated that a wavelength of
500 nm corresponds with an
effective temperature of about
5800K. Such a temperature,
deduced by calculation from a
measured colour, is called the
colour temperature and it is used
to indicated the colour of for
instance tube lights. By
convention we judge colours
towards the yellow/orange side of
the spectrum as 'warm' while
colours towards the blue side are
said to be 'cold' although the colour temperatures sugests the opposite. So, a 'warm'
colour will have a low colour temperature while a 'cold' colour will have a high colour
temperature.
