Newtons corpuscular theory of light - Wave Optics Video Lecture - Class 12

Newton's corpuscular theory today we're
going to learn about Newton's
corpuscular theory Sir Isaac Newton's
corpuscular theory was one of the
earliest scientific attempts at
understanding the nature of light even
though it was originally set forward by
Pierre Gassendi it was Newton who had
later developed and proposed the
corpuscular theory of light way back in
the 17th century however after 100 years
of existence it later gave way to a more
popular Huygens wavefront theory that
could explain some of the limitations of
Newton's corpuscular theory Newton's
corpuscular theory of light states the
following light consists of corpuscles
which are a stream of discrete tiny
light and perfectly elastic particles
every luminous source like the Sun a
lamp or a candle amidst these corpuscles
these corpuscles travel in straight
lines in all possible directions the
rate at which these corpuscles travel
may differ depending on the medium in
which they disperse the vision of human
beings is a consequence of these
corpuscles falling on the retina of the
eyes various colors of light are due to
the difference in sizes of these
corpuscles these corpuscles could
perfectly explain the concepts of
reflection and refraction of light the
reflection of light which consisted of
corpuscles is just like the reflection
of a perfectly elastic ball consider the
case of a perfectly elastic ball that
hits the wall which is a rigid plane
when this ball hits the wall normally it
bounces back and travels along the same
path that it takes during the throw
however when this ball is thrown at an
angle to the wall it bounces back and
away from the wall at an equal angle
with respect to the normal however it
takes the opposite direction the angle
of incidence I of the ball is equal to
the angle of reflection our reflection
of corpuscles of light follows the
same rules that reflection of this
perfectly elastic ball exhibits in other
words each of the corpuscles behaves
just like an elastic ball this means
that when corpuscles hit the surface
normally they travel along the same way
back and when they hit the surface at an
angle they are repelled near the surface
and reflected back such that the angle
of incidence I is equal to the angle of
reflection are according to Newton the
refraction of light was due to the
supposed change in the speed at which
they travel thereby causing a resultant
change in the direction whenever these
corpuscles enter from say a denser
medium to a rarer medium
although Newton's corpuscular theory of
light could successfully explain the
reflection of light his assumption of
higher velocity of light in denser
medium as compared to the rarer medium
has been disproved he was also unable to
validate his supposition that various
colors of light are due to the
difference in sizes of these corpuscles
for these reasons the hypothesis was
rendered baseless the biggest limitation
of Newton's corpuscular theory of light
was that it could not illuminate the
phenomena of interference diffraction
and polarization of light this is why
the theory was later abandoned in favor
of Huygens wave theory of light which
proved that the light travels in the
form of waves
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