Light and Optics
In 1835 Sir Charles Wheatstone
read a paper on the 'Prismatic Analysis of Electric Light' ยท
before the British Association meeting at Dublin. He demonstrated
the fact that the spectrum of the electric spark from different
metals presented more or less numerous rays of definite
refrangibility, producing a series of lines differing in position
and colour from each other and that thus the presence of a very
minute portion of any given metal might be determined. 'We have
here', he said, 'a mode of discriminating metallic bodies more
readily than by chemical examination, and which may hereafter be
employed for useful purposes'.
This remark is very
typical of his farsightedness into the practical utility of any
known scientific fact. His 'polar clock' was another instance of
this trait of his genius. When Brewster discovered that the plane
of polarisation of the light from the sky is always 90 degrees
from the sun, Wheatstone devised a clock by which it was possible
to tell the hour of the day by the light from the sky though the
sun might be invisible.
He also conducted
experiments in order to calculate the speed of light and produced
a figure of almost 250,000 miles per second - by far the most
accurate estimate of that time.
