# Physics 1: Particle Theory of Light by YcZNzQ2v

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Physics 1:
Particle Theory of Light

Group 1
II – Camia
Sir Delfin Angeles
Topics to be discussed:
 Corpuscular Theory of Reflection
 Newton’s Arguments
 Corpuscular Theory of Refraction
Unusual Terms:
 Corpuscle - a particle of matter, as an electron, proton, or
atom
 Electromagnetic radiation – produced by the movement of
electrically charged particles. They travel through empty
spaces, air, and other materials
Contributors to the Discovery of
Atoms:
1.    Leucippus
– when he was walking with his student Democritus, they observed that
water looks like one solid object., but when you touch water, the particles can be
seen. Same goes for the sand at the beach
– suggested that matter can be broken down into smaller pieces until they
become indivisible
– called these tiny particles “atomos” which means indivisible
2.     Aristotle
– did not agree with Leucippus’ and Democritus’ theory
– “Why does matter not fall apart when blown by the wind or washed by
water, if they are composed of tinier particles?”
– stated that matter is made up of 4 elements; fire, water, wind, and earth
(postulated by Empedocles in the fifth century BC)
– matter was continuous all of one piece
– other scientists agreed with Aristotle. It was not until 18th century when
the atom’s indivisibility was retested
Contributors to the Particle Theory
1.   John Dalton
– studied the works of French chemists Antoine Lavoisier
and Joseph Louis Proust, and made the following
conclusions/postulates in 1808
– All atoms of the same element are identical, but
they are different from the atoms of other elements. They are
unchangeable. According to him, “The atoms never can be
metamorphosed one into another by any power we can control.”
– During chemical reactions, atoms are neither
created nor destroyed (Lavoisier’s Law of Conservation of
matter)
– Atoms which form a compound always combine in
definite whole number proportions (Proust’s Law of Definite
Composition).
Contributors to the Particle Theory
2.   Robert Boyle (1627-1961)
– postulated that gases are composed of discrete particles
separated by a void
3.   Isaac Newton
– “God in the beginning formed matter, in solid, massy, hard,
impenetrable, movable particles…”
Particle Theory of Matter
   Also known as the Kinetic Theory of Matter
   A theory which states that matter is made up of small particles which are moving
continuously
   Around 17th century, experimental evidence in support of particulate theory
accumulated
   The degree to which the particles move is determined by the amount of energy
that they have and their relationship to other particles

Matter
The Particle Theory states that:
1.   Matter is made up of tiny particles (atoms and molecules).
2.   Particles of matter are in constant motion.
3.   Particles of matter are held together by very strong electric forces.
4.   There are empty spaces between the particles of matter that are very
large compared to the particles themselves.
5.   Each substance has unique particles that are different from the particles
of other substances.
6.   Temperature affects the speed of the particles. The higher the
temperature, the faster the speed of the particles.
The Particle Theory explains that:
1. Pure substance are homogenous. (One phase
– one unique kind of particle)
2. Physical Changes – melting, evaporation,
sublimation, dissolving, etc.
3. Characteristic Physical Properties – density,
viscosity, electrical and thermal conductivity,
etc.
What is Light?
 Light is a range of electromagnetic radiation
that is visible to the human eye.
 In Physics: Light refers to electromagnetic
radiation of any wavelength whether visible or
not.
Corpuscularianism
alchemist Geber
   It is a postulate which states that all
physical bodies possess an inner and
outer layer of corpuscles
   Used by Newton in developing the
Particle Theory of Light
Who is Isaac Newton?
   English physicist, mathematician,
astronomer, natural philosopher,
alchemist, and theologian
   He is became famous because of his
works in mathematics, optics,
mechanics, and gravitation
Corpuscular Theory of Light
   It is a theory made by Isaac Newton which states that
light is made up of small corpuscles that travel in a
straight line (rectilinear propagation) with a constant
velocity and possess kinetic energy
Corpuscular Theory of Reflection
   A particle incident on a surface has components of its
velocity in both the X and Y directions. The X
component must then remain the same if the force
on the particles acts perpendicular to the surface.
The Y component of velocity is just reversed since
the kinetic energy remains constant. This would make
the angle of reflection equal to the angle of incidence
Corpuscular Theory of Refraction
   The thought that light bends towards the normal when moving
from air to water can be demonstrated. Newton believed that
water attracted light particles, therefore, the particle’s velocity
increased. This increase in velocity would cause its path to bend
towards the normal.
    This could lead Newton to predict that the speed of light in water
was greater than in air. In 1850, Foucault showed that light
travelled slowly in water than in air. The particle theory seems to
be wrong.
   The mass of the source remains unchanged due to emission of
material particles, via the corpuscles.
   Simultaneous refraction and reflection of light from transparent
surfaces could not be accounted for.
   The speed of light in a denser medium turns out to be greater than
the speed of light in a rarer medium, according to Newton's theory.
Experimentally, its exact opposite is found to be true.
   Other phenomena like interference, diffraction, polarization, etc.
could not be explained through Newton's corpuscular theory.
The Clash of the Nerds!
May proofs ako!
Wala kayong laban sa
theories ko!             And BTW,
Who’s better and more
handsome?

vs.
References
   http://www.le.ac.uk/se/centres/sci/selfstudy/particle01.html#propertiesofmatter
   http://www.clickandlearn.org/Gr9_Sci/Particle_Theory.htm
   Sir Montales’ PPT Presentation
   http://www.indicareer.com/entrance-exams/mht-cet/physics/Wave-Theory-of-Light-1.html
   http://schools.cbe.ab.ca/b858/dept/sci/teacher/zubot/Phys20notes/Chapter14/1chapter14/1ch14.
htm
   http://arxiv.org/ftp/physics/papers/0411/0411110.pdf
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