Since all the wavelengths of
the visible light is present, it is a continuous spectrum. The rainbow is
a natural example of this spectrum.
However, this visible spectrum
occupies only a small part of the much bigger, electromagnetic spectrum. Despite it being
in a small range, it is of grave importance. Without it, life on earth will not able to
sustain. Nearly half the sun's energy emitted exists in the form of visible light. The
many living organisms have been differentiated in such a way that they are sensitive to
the sun's emitted energy. In other words, without such adaptations life will cease to
continue. You will be looking at how light can be used in the later sections.
Wavelengths &
Colours
The light that is visible to
the human eye comprises of 7 colours, namely - red, orange, yellow, green, blue, indigo,
violet. If you find it hard to remember, use the nemonic ROYGBIV . The first letters of
the colours made up the nemonic. Another alternative is to remember Richard
Of York Gave Battle In Vain.
Each colour corresponds to a
different wavelength. Orange light has a wavelength of around 600 thousands millionths of
a meter, or 600 nanometers. Green light has a wavelength of around 500 nanometers, and
violet around 400 nanometers. The colours are arranged in the spectrum according to their
varying wavelengths. The figure below shows you how the colours reside.
Primary & Secondary
Colours
Out of the seven colours,
there are certain colours which are primary , i.e. they are the basic colours. There are
also secondary colours , i.e. they are created by means of combining primary colours.
The primary colours of light
are red, blue and green. Primary colours of dyes are yellow, cyan and magnenta.
Certain colour combinations
can be obtained as follows ;
Do note that primary colours
of dyes when mixed will yield a black colour but only primary colours of light will give
you white. Have fun.
