Newton vs Huygens: corpuscular vs wave models of light explained and refuted
Summary
TLDRThis video script delves into the historical debate on the nature of light between 17th-century scientists Christiaan Huygens and Isaac Newton. Huygens proposed a wave theory, while Newton championed the corpuscular theory. The script explores how each model explained light phenomena like reflection, refraction, and polarization, and how experiments by Young and others eventually favored the wave theory. It concludes with the modern understanding of light's wave-particle duality, highlighting the scientific evolution from Newton's influence to quantum mechanics.
Takeaways
- π In the 17th century, the nature of light was debated, with Christiaan Huygens and Isaac Newton proposing opposing theories.
- π Huygens argued that light was a form of a wave, while Newton believed it was made up of particles, called corpuscles.
- π§ͺ Both scientists used their models to explain behaviors of light such as reflection, refraction, and polarization.
- πͺ Newton's corpuscular theory explained reflection by considering light particles as tiny elastic masses that obey the laws of physics.
- π Newton also used his theory to explain refraction, suggesting that light particles interact with matter, increasing their velocity in denser substances.
- π Newton's prism experiment demonstrated that white light is made up of different colors, each with particles of different sizes.
- π Huygens' wave theory explained reflection and refraction using the concept of wave fronts and wavelets, as well as diffraction, which Newton's theory could not.
- π Huygens' model could also explain diffraction and polarization better than Newton's corpuscular theory.
- π Despite the advantages of Huygens' wave theory, Newton's corpuscular theory initially gained more acceptance due to Newton's scientific stature.
- π¬ The wave theory of light eventually prevailed in the 19th century with key experiments by Thomas Young and LΓ©on Foucault, disproving Newton's model.
- π‘ Light is now understood as having a wave-particle duality, combining aspects of both Huygens' and Newton's theories, as demonstrated by Einstein's work on the photoelectric effect.
Q & A
What were the two main theories about the nature of light in the 17th century?
-The two main theories were the wave theory proposed by Christiaan Huygens and the corpuscular theory proposed by Isaac Newton.
What experiment in 1679 helped establish that light travels at a finite speed?
-The experiment by La Roma, who studied the eclipses of one of Jupiter's moons, helped establish that light travels at a finite speed.
How did Newton explain the reflection of light using his corpuscular theory?
-Newton explained reflection by stating that light particles, or corpuscles, would bounce off surfaces with the same angle of incidence as the angle of reflection, due to elastic collisions.
What was Newton's explanation for the refraction of light?
-Newton believed that light particles would slow down when entering a denser medium, causing them to bend towards the normal due to attractive forces, and then speed up again when exiting the medium.
Why did Newton's corpuscular theory fail to explain certain phenomena like diffraction?
-Newton's corpuscular theory could not adequately explain diffraction because it did not account for the wave-like behavior of light spreading out after passing through a small opening.
How did Huygens' wave theory explain the reflection and refraction of light?
-Huygens' wave theory explained reflection and refraction by considering the wavefronts produced by secondary wavelets at the boundary of the medium, which then interfere constructively to form new wavefronts at different angles.
What experiment by Thomas Young in 1801 challenged Newton's corpuscular theory?
-Thomas Young's double-slit experiment demonstrated interference patterns, which supported the wave theory of light and challenged the corpuscular theory.
What experiment in 1854 provided evidence against Newton's theory of light speed in different media?
-In 1854, an experiment by Augustin-Jean Fresnel showed that light travels slower in water than in air, which contradicted Newton's expectation that light would speed up in denser media.
What is the modern understanding of light, as per Maxwell's electromagnetic theory?
-Maxwell's electromagnetic theory describes light as a transverse wave composed of oscillating electric and magnetic fields, which travels through space at the speed of light.
How does the wave-particle duality concept relate to the historical debate between Newton and Huygens?
-The wave-particle duality concept, introduced by Einstein's photoelectric effect, suggests that light behaves both as a wave and as a particle (photons), thus indicating that both Newton's and Huygens' theories had elements of truth.
Outlines
π¬ The Great Debate of Light: Waves vs. Corpuscles
This paragraph introduces the historical debate on the nature of light during the 17th century, focusing on the contrasting theories of Christiaan Huygens and Isaac Newton. Huygens proposed that light behaves like a wave, while Newton believed light was composed of particles, or 'corpuscles'. The paragraph sets the stage for a deeper exploration of these theories and their implications for understanding light's behavior, such as reflection, refraction, and polarization. It also mentions the experiment by La Roma in 1679, which established that light travels at a finite speed, a key discovery in the scientific understanding of light.
π Newton's Corpuscular Theory: Reflection, Refraction, and Prism Experiment
This paragraph delves into Isaac Newton's corpuscular theory of light, explaining his views on reflection and refraction. Newton posited that light particles, or corpuscles, behave like tiny, perfectly elastic particles traveling at high speeds, obeying the laws of physics. The paragraph describes Newton's explanation of the law of reflection and his concept of how light bends when it enters a different medium, attributing this to attractive forces within the material. It also discusses Newton's famous prism experiment, which dispersed white light into a spectrum of colors, supporting his idea that light is made up of different-sized corpuscles, each corresponding to a color in the visible spectrum.
π Huygens' Wave Theory: Reflection, Refraction, and Diffraction
The paragraph shifts focus to Christiaan Huygens' wave theory of light, which describes light as emanating in wave fronts that generate successive wave fronts. It explains how Huygens used this model to explain reflection and refraction, using animations to visualize the wavelets forming at boundaries and demonstrating how both reflection and refraction can occur simultaneously. The paragraph also touches on diffraction, a phenomenon that Huygens' wave model could explain but Newton's corpuscular theory could not, and mentions the lack of a satisfactory explanation for double refraction from either model at the time.
π The Rise and Fall of Theories: From Corpuscles to Waves
This final paragraph summarizes the historical reception of the two theories, noting that Newton's corpuscular theory was more widely accepted due to his scientific stature and the lack of a mathematical explanation for Huygens' wave theory. It discusses the key experiments in the 19th century that eventually led to the downfall of the corpuscular theory: Thomas Young's double-slit experiment demonstrating interference, a phenomenon consistent with the wave model, and an experiment by Augustin-Jean Fresnel that showed light travels slower in water than in air, contradicting Newton's predictions. The paragraph concludes with a modern understanding of light as having wave-particle duality, acknowledging the contributions of both Huygens and Newton to our comprehension of light.
Mindmap
Keywords
π‘Reflection
π‘Refraction
π‘Diffraction
π‘Interference
π‘Polarization
π‘Wave-particle duality
π‘Corpuscular theory
π‘Wave theory
π‘Ether
π‘Scientific Revolution
Highlights
In the 17th century, the nature of light was a mystery, with two opposing theories by scientists Christiaan Huygens and Isaac Newton.
Huygens proposed light as a wave, while Newton believed in light being composed of particles called corpuscles.
Newton's corpuscular theory explained reflection and refraction by treating light particles as tiny, perfectly elastic objects.
Huygens' wave theory suggested that each wavefront generates new wavelets, creating a pattern of spherical waves.
Newton's model could not explain phenomena like diffraction, where light bends around obstacles.
Huygens' wavefront model provided a better explanation for diffraction, showing how waves bend around barriers.
Newton's theory was favored due to his scientific stature and the lack of a mathematical framework for Huygens' theory.
The wave theory gained support with Thomas Young's double-slit experiment demonstrating light interference in 1801.
The speed of light experiment by Foucault in 1854 contradicted Newton's theory, supporting the wave nature of light.
Maxwell's electromagnetic theory later described light as a transverse wave of oscillating electric and magnetic fields.
Einstein's photoelectric effect in 1905 showed light also has particle-like properties, introducing the wave-particle duality.
Huygens and Newton's theories were both partly correct, illustrating the complexity of understanding light's nature.
The historical debate between wave and particle theories of light has led to a deeper understanding of quantum mechanics.
The scientific community's initial preference for Newton's theory highlights the influence of a scientist's reputation.
The evolution of light theories from the 17th to the 20th century reflects the dynamic nature of scientific knowledge.
Huygens' wave model was able to explain reflection and refraction more consistently than Newton's corpuscular theory.
The wave-particle duality of light is a fundamental concept in modern physics, bridging classical and quantum theories.
The historical journey of light theories exemplifies the scientific method's iterative process of hypothesis, experiment, and revision.
Transcripts
like we all see it and its effects
reflection refraction just to name a
couple but what actually is it now today
we've got some good answers but back in
the 17th century
nobody scientists had any idea but to
scientists at the time had some IDs
however they were in complete opposition
so today we're gonna look at their two
models and how they explain various
light behaviors and see who won out in
the end
just a tune
[Music]
now there were two great scientists in
that time christiaan huygens for Holland
and Isaac Newton from England who lived
roughly around the same time in the 17th
century right at the midst of what we
now call the Scientific Revolution and
in the latter half of that century a key
experiment took place that established
that life wasn't some instantaneous
substance but that like travel at a
finite speed so to speak and that was
the experiment by la Roma in 1679 as he
studied the eclipses of one of the moons
of Jupiter now I did a video on that
that discusses that not pop a
description just above but the question
was what was light actually made up of
now Christian Huygens argue that light
was a form of a wave Isaac Newton
however believed that light was actually
made up of particles which he called
corpuscles now both used their models to
explain various behaviors of Lights such
as reflection and refraction and
polarization and what I plan to do is
use their models to explain these
behaviors now I want to stress though
that what I'm presenting is not the real
explanation of the behavior of light but
how these men believed it to be so let's
start with Newton now Newton believed
that these corpuscles of light were tiny
perfectly elastic particles traveling at
very high speeds they behaved with the
laws of physics like any masses such as
balls and planets but since there was so
tiny when two light beams intersected
they did not scatter with each other so
let's have a look how he explained
various phenomena so let's talk about
Newton's understanding of reflection
using this corpuscular method I'm going
to assume you understand the law of
reflection that is the incident angle
equals of the reflected angle now here's
our particle it's coming in and it's
bouncing off the surface and of course
it's coming off of the other side now
let's have a look at the path - here's
our path and Newton said well hold on
it's moving in two directions it's
moving horizontally but it's also moving
vertically so horizontally he's saying
well that's going to be exactly the same
velocity it's not gonna change
velocities in terms of the horizontal
motion but because it's an elastic
collision as far as Newton understood it
he said to all the
vertically is the same verb as the
velocity vertically on the other side
obviously in the opposite direction and
so when you resolve those two vectors
you're going to see that the actual
angle coming in is the same as the angle
alpha and so there is Newton's
understanding of reflection let's now
look at refraction so he is our particle
and it is also moving and in this case
our particle is not bouncing off the
surface it is now entering into the
surface and again in this case Newton's
nose that it bends towards the normal I
assume you understand the nature of
refraction at least in that terminology
and so he said again horizontally we
have motion in that direction and we
still have that velocity also in that
direction once we go into the surface
why doesn't Bend well it's a particle
and so this particle interacts with the
matter and so as a result there's these
attractive forces now while sits inside
the matter those forces cancel out so
therefore the path remains straight same
outside as well but the issue is what
happens at the interface and so Newton
argued said well hold on what's going to
happen here is that there's a source of
attraction and so what that means is
that it's going to be pulled in and so
as a result if the velocity of the
situation here is that value here he's
saying look the matter interacts with it
and pulls it in stronger and as a result
it's going to have a velocity that is
bigger and so when you resolve those two
vectors you're going to get an angle
here like so and an angle here like so
and here's the critical point if the way
that Newton saw it is that the velocity
increases as it passes through the
substance and you can see that by just
looking at the mathematics of these
vectors is that the vector is now larger
and so that's a critical point here with
Newton's corpuscular theory is that he
assumed that the velocity of the core
bustles is actually greater in the
denser substance and because of the fact
that denser substances have more
particles there
go traveling faster and therefore you
have different refractive indexes which
is about the relationship of the
velocities with the outside and the
inside but I want you to note though we
often see reflection and refraction
happening for example if you look at a
glass you see reflection but you also
see through it to your self refraction
and unfortunately Newton's corpuscular
theory doesn't allow for an explanation
for that so now let's have a look at his
famous experiment to do with prisms and
many of you may have be recognized
something similar into this image of
what Newton did and so we had the light
passing through a prism and of course it
dispersed and we produced a rainbow now
how did he explain this so let's have a
closer look and so here is our white
light and here we look at just the path
of the red corpuscle well if it's a red
corpuscle we need a corpuscle
in place and so what Newton argued is
like this corpuscle is reasonably large
and so therefore the material interacts
with it bends it as we discussed it
before in refraction and only bends it a
certain amount because of the size of
the Capasso
but what about the other colors well
they also made up of corpuscles but they
progressively get smaller as we move up
the spectrum and so therefore the
smaller the particle the smaller the
corpuscle the more effect the
interaction of the material of the glass
and so it bends more so he was able to
show that white light isn't a single
entity it's actually made up of
different colors why because different
colors have different size of corpuscles
and so by using a prism he was able to
spread them out and therefore show the
colors of the rainbow now here I've got
five representative examples of our
colors of the rainbow and you say all
aren't there supposed to be seven well
really the number seven was actually put
in placement by Newton why seven well
actually he thought seven was a nice
number to spread the colors of the
rainbow out into it because in the Greek
mythology seven was a mystical number
and so that's why we have seven colors
of the rainbow it has nothing to do with
the fact that there is only seven colors
in the Roma there's actually an almost
infinite number of colors of in the
rainbow now unfortunately he failed to
come up with an adequate explanation for
a
a phenomena and that was diffraction you
see when light passes through a small
hole it spreads out and if light was
made of particles why would it do that
and then there was the observation by
Erasmus battlin who observed a double
refraction of light through it calcite
crystals now two images appeared and
they moved as you turn the crystal maybe
the light was split into two types and
Ethan's best response was on this idea
was that that the cop fossils had some
sort of sides but really that wasn't
satisfactory so now let's have a look at
Huygens heigen believed that light
source emanated in the form of wave
fronts and that there were spherical and
that each wave front would generate the
next wave front and so forth well let me
explain this so here I have a wave I'm
going to imagine here is a wavefront or
a set of a ring of waves after you've
dropped a stone in the pond and this is
the way that heigen tried to imagine why
there were successive wave fronts so
this wave front he will produce a
particular wavelet in a particular
direction now it's actually spherical
but we've got a two-dimensional aspect
here now we know of course that sphere
goes backwards and side words and at
least as far as heigen he really didn't
explain why are we only having this one
he in this direction but we're going to
use that as our example now obviously
that's not the only point there are lots
of points all around that that also
produce these wavelets now I've only got
a certain number here but there are
actually many many more but what happens
is that all of those add up to produce
our next wavefront and then of course
you get your successive wave fronts
after that each being produced by the
one that was previous if we then look at
the direction of the wave fronts you'll
see that the path the Ray so to speak is
perpendicular to the wave fronts at all
junctions and now what we're going to do
is we're going to use Christian Huygens
understanding of wave fronts to see how
he explained reflection and refraction
but in this case we're going to use an
animation to help us understand that and
I'll use this animation from water faint
and I'm going to put a link in the
description below if you want to have
more at some of his great animations so
here you can see the wave front coming
in and of course it's moving from the
left side of the screen now watch what
happens when it hits the surface you can
see little wavelets being formed and as
a result it produces a wave front that
is moving off at exactly the same angle
then the wave front that arrived so
here's a wave front coming in and in
this case you'll see that our wave front
in this case produces these little
wavelets that are now passing through
the material but because the wavelets
are now moving slower you'll see that
the wave front that's produced when they
add up is actually moving at a different
angle towards the normal and you can see
that now and now what you're going to
see is both reflection and refraction
occurring at the same time and you'll
see that Huygens model adequately
explains why that occurs we have the
wavelets forming at the boundary that
are reflecting and also wavelets bound
happening at the boundary that are
refracting and you see both take place
the key thing here is is that Huygens
model also was able to explain
diffraction let me explain so as you can
see from this great animation from Phet
you see the wave fronts hitting the
barrier but there's a small opening but
because the wave fronts are made up of
successive little wavelets the one
wavelet that meets the opening continues
and so therefore you get these
concentric circles on the other side of
the wall
you see diffraction and the waves are
bending around the wall and what about
the double refraction now Huygens didn't
really have an answer but it was later
as polarization was further studied in
the 19th century and a wave model best
describes the behavior of polarization
so in essence Huygens saw light is a
form of a longitudinal wave traveling
through space now what would the medium
be well he believed there existed this
unseen medium called the ether which
allowed light to travel through space so
let's summarize so in terms of
reflection in terms of their models we
can argue that Newton did a pretty good
job but so did Hogan in terms of
refraction yes Newton did a reasonably
good job of understanding wide bends
as did Huygens what about diffraction
well diffraction is problematic in terms
of mutants oh no that doesn't work there
but Huygens understanding definitely
works polarization which is the double
refraction that was observed neither
could really provide a good explanation
as to why they occurred and then we go
interference now in terms of
interference that wasn't really studied
properly until the 19th century
Newton's understanding doesn't help us
understand it at all
whereas Huygens understanding of waves
does so how did the scientific community
respond well Newton's corpuscular theory
was the one that held sway in a
scientific community
and there are really two reasons for
this now first Newton was a huge man of
scientific stature his Principia are we
discussed the laws of motion and the
calculus that supported it was hugely
popular and accepted now who was one to
argue with him on his use of light now
Newton did have his critics of the
Cabasa Coulomb model and one of his most
vocal critics was Francis Bacon who
supported the wave model and it's
possibly the reason why I'm Newton
delayed publishing his book optics until
Bacon died now secondly Hogan was lesser
known and he also only provided a
geometric explanation for light and not
a mathematical one and that was what's
needed if it was to be accepted by the
scientific community and that really
didn't come until the work of Fresnel in
the early 1800s and so the capacitor
theory stood for some time until that is
two key experiments in the 1800s
now the first was in 1801 by Thomas
Young with his double slit experiment
again I have a video already on that and
I encourage you to look at the link
above but the key finding here is that
he was able to demonstrate interference
using the wave model of light however
there are still some resistance in the
scientific community to reject the
corpuscular theory and then in 1854 coal
in a modified setup of his apparatus to
measure the speed of light determined
that light traveled slower in water than
air now this was in direct opposition to
Newton's model where he expected the
light to speed up but only ways would
slow down in water and thus that spelled
the end of the cost
theory it's funny how a single
experiment can destroy a whole world
constructive model but science works
that way light was a wave after all
now both models actually are flawed and
they've been replaced with Maxwell's
electromagnetic theory yes light is a
wave or it's a transverse wave composed
of oscillating electric and magnetic
fields and I encourage you to check out
my video on Maxwell so is that how the
story ends well no in 1905 Einstein
published his work on the photoelectric
effect which demonstrated that light
travelled in discrete packets which he
called quanta or photons as we now call
them so light troubles as a wave and a
particle now we refer to this as the
wave particle duality of light so in a
roundabout way Newton and Huygens were
both right after all I hope that's
giving you a better understanding of the
history behind understanding of the
nature of light check out my other
videos on Maxwell's theory as well as
the history behind determining the speed
of light please like share and subscribe
drop a comment down below if this video
has been particularly helpful my name is
Paul from high school physics explained
take care bye for now
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