Hundred Great Muslims

Hundred Great Muslims
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His explanation does not depend upon mere hypothesis or supposition, but is
plainly based upon anatomical investigations as well as geometrical discussion".
His works on optics influenced the greatest Western scientists and paved
the way for later discoveries and developments in the field of optics. He has
examined the refraction of light rays through transparent objects, including air
and water. In experimenting with spherical segments (glass vessels filled with
water) he has forestalled the theoretical discovery of magnifying lenses, which
was made three centuries later in Italy. He also prepared the ground for Snell
and Descartes to establish the law of sines, six centuries later.
Among other things he discussed was the 'propagation of light and colours,
optic illusions and reflection, with experiments for testing the anglesof incidence
and reflection'. His 'Alhazen Problems' in optics are still known throughout the
West. 'In a spherical concave or convex, a cylindried or conical mirror to find the
point from which an object of given position will be reflected to an eye of given
position. It leads to an equation of the fourth degree which Alhazen solved by
the use of a hyperbola.
He made a number of monumental discoveries in the field of optics,
including one which locates retina, as the seat of vision. This discovery falsified
the earlier contention of the Greek scientists that eye sends out visual rays to
the object of the vision.
According to him, the impression made by light on 'retina is conveyed to
the brain through optic nerves. He also explained how only one object is visible
when seen from both the eyes, because the 'visual images are formed on symmetrical
portions of the two retinas'. The optical illusions, according to him, are
due to rays of light suffering from reflection or refraction. "He is perfectly
aware", writes a Western orientalist, "that the atmosphere decreases in density
with the increase of height, and from that consideration he shows that a ray of
light, entering it obliquely, follows a curvilinear path which is concave toward
the earth, and that, since the mind refers the position of an object to the direction
in which the ray of light from it enters the eye, the result must be an illusion as
respects the starry bodies; they appear to us, to use the Arabic term, nearer to
the zenith than they actually are, and not in their true place." He has found
out a wonderful optical illusion in the twilight when he sees stars. Sun and
Moon before they have risen and after they have set. He has explained that
greater the density of atmosphere, the greater the curvature of a ray of light.
"To this refraction he truly refers the shortening, in their vertical diameter, cf
the horizontal Sun and Moon; to its variations he imputes the twinkling of the
fixed stars". He quite accurately determined the height of the atmosphere as
nearly 58lh miles. Describing his lasting contribution to optics, John William
Draper states; "All this is very grand. Shallwe compare it with the contemporary
monk miracles or the monkish philosophy of Europe? It would make a profound
impression if communicated for the first time to a scientific society in our own
age". Commentaries on Alhazen's optics were written by oriental writers and his