Nature-of-Light.pptx

9/3/20XX Presentation Title 6
Warm Up Activity

WORD GAME
Each of the letters of the alphabet
corresponds to a number. Using these
numbers, decode the following words
to identify the different words in our
lesson today.

1. 23- 1- 22- 5
Wave

2. 12-9-7-8-20
Light

3. 19-15-21-14-4
23-1-22-5
Sound waves

4. 19-15-14-18
SONAR

5. 21-12-20-18-1-19-15-21- 14-4
23-1-22-5
Ultrasound
Waves

What is Wave?
is a disturbance in a medium
that carries energy without a
net movement of particles.

What is Optics?
A branch of physics that involves
the behavior and properties of
light, including its interactions
with matter and the construction
of instruments that use or
detect it.

What is Light?
is the smallest amount of
energy that can be transported.
It has wave-particle duality: it
is both an electromagnetic
wave and a particle, known as a
photon.

Is light a Wave or
a Particle?

Guide Questions:
 Who are the
scientists mentioned
in the video?
 What are their
contributions to the
field of Physics
specifically in
Optics?

Trace the
History..

Let’s have an activity..

Rubrics For The Presentation

EUCLID (300BC)
 studied the rectilinear propagation of light as well as the law
of reflection (book “ Catoptrics”)
 referenced the apparent bending of objects partly
immersed in water
Plato’s Republic

CLEOMEDES (50AD)
 studied refraction of light and later Ptolemy (130 AD)
 tabulated fairly precise values of the angles of incidence
and refraction for several media
Ptolemy
 Romans also knew about burning by magnifying glasses.
Several glass and crystal spheres were traced in Romm ruins.
This suggests that some Romas artisans may have used
magnifying glasses to facilitate their very fine detailed work

Ibo-al-Haitham, also known as Alhazen (1000 AD)
 studied reflection of light by place, spherical and parabolic
mirrors and accedal in putting the angles of incidence and
reflection in the same plane normal to the interface. Alhazen's
work was translated in Latin and influenced the works and
writings of later researchers.
Bacon (1215-1294)
initiated the idea of using lenses for correcting vision and
hinted at the possibility of combining them to form a telescope.

Leonardo da Vinci (1452-1519)
 described the camera obscura, which was propelled by
Giovanni Battista Della Porta (1535-1615), who discussed
multiple mirrors and combinations of positive and negative
lenses in his Magia naturalis (1589).
Galileo Galilei (1564-1642)
 widely credited for designing the first refracting telescope,
though The Hague archives suggest that the credit should go
to a Dutch spectacle maker Hans Lippershey (1587-1619) as
he reportedly filed application for a patent on the device.

Kepler
 Observed the phenomenon of total internal reflection
Snell
 gave the law of refraction, which was given the formulation
in terms of sines by Descartes (1637). He viewed the light
beam as pressure transmitted by an elastic medium. In
essence, this derivation assumed corpuscular model of light,
which is usually attributed to Newton, probably because of
the popularity of his Opticks.

Descartes (1637)
 He viewed the light beam as pressure transmitted by an
elastic medium. In essence, this derivation assumed
corpuscular model of light, which is usually attributed to
Newton, probably because of the popularity of his Opticks.
Pierre de Fermat (1605-1665)
 enunciated his principle of least time and derived Snell's
law of refraction. He showed that the ray of light would
bend towards the normal, if the velocity of light in the second
medium were lower. This contradicted corpuscular theory.

Robert Boyle (1627-1691) and Robert Hooke (1635-1703)
 observed beautiful coloured rings in thin films. (These were
termed Newton's rings because Newton explained their
formation in terms of his corpuscular model.
Francesco Marie Grimaldi (1618-1663)
 the form of bands of light in the shadow of a rod illuminated
by a small source.

Robert Hooke (1635-1703)
 He also explained the existence of Newton's rings in terms of
the 'interaction" between the light reflected from the front and
back surfaces. He proposed the idea that light was a rapid
vibratory motion of the medium and propagated at a very
high speed. He also observed that "every pulse or vibration
of the luminous body will generate a sphere". This marked
the beginning of the wave.

Isaac Newton (1642-1727)
 This became evident in his work on dispersion of light-
breaking up of light in constituent colours when light was
made to undergo refraction through a triangular glass prism.

 regarded optics as experimental philosophy, laid greater
emphasis on direct observation than speculative
hypotheses. This made him unsure about the nature of light;
initially he could not decide whether light emitted by a source
consisted of a stream of very small particles which
stimulated the sense of sight when entering the eye -
corpuscular theory of light-or vibratory motion of the
medium propagating at a very large speed-wave theory of
light.

 To explain his observed results, he simultaneously embraced
wave as well as corpuscular (emission) theories. He argued
that the corpuscles of light associated with different colours
excited the ether-all pervading massless fluid-into
characteristic vibrations. But he became committed to
corpuscular theory of light when he explained rectilinear
propagation of light, which resulted in the formation of sharp
shadows. He also gave simple explanation for the laws of
reflection and refraction, formation of coloured fringes in thin
films, among others. Newton’s theory of light was therefore
widely accepted by the scientific community.

Chestian Hotypes (1629-1695)
 forward the wave theory of light. He demonstrated that when
two beams of light intersected, they emerged changed.
 observed the phonmenon of double reaction is calcite. It was explained by
Huygens, who alse showed that light effectively slowed down on entering the
demer media. But this theory did not receive acceptance of most scientists,
who continued to adhere to Newton's corpuscular theory for more than a
century for several reasons The foremost of these were:
> rectilinear pogonion of fight,
>light (from the sun) could travel through vacum,
Erasmus Bartholinas (1625-10

Thomas Young (1773-1829)
 He performed a very significant and now famous double shit
interference experiment, which could be explained only on the
basis of wave model of light. In 1802, he gave an explanation of
the formation of Newton's rings observed by Boyle.
 discovered polarisation of light
Malus (1775-1812)

Augustine Freanal (1788-1827)
 presented satisfactory explanation of the diffraction patterns
resulting from different types of obstacles, edges and apertures
on the basis of wave theory, He was also able to account for
rectilinear propagation of light in homogeneoun isotropic
media, dupelling Newton's main objection. This was a big step
in the right direction to understand the nature of light.
 performed a brilliant experiment on interference of linearly polarised light. But
they struggled to provide satisfactory explanation of their observations because
they treated light as longitudinal waves, in analogy with sound waves in air.
Fresnel and Dominique Francois Jean Arago (1786-1853)

James Clerk Maxwell (1831-1879),
 derived a wave equation starting from his set of four equations,
which brilliantly summarised all the then known laws of electricity
and magnetism, and predicted the existence of transverse
electromagnetic waves.
 Maxwell calculated the speed of electron waves to be 3.1074 x 10 8
ms -1 .This was amazingly close to the then most pres known value
of 3.14858 x 10 8 ms -1 speed of light obtained from optical
experiments by the French scientist Armand Fizeua (1819-
1896).Thus, he concluded that light propagated as an
eletromagnetic wave.

Jean Foucault (1791 1868)
 provided further evidence of the inadequacy of the Corpuscular
theory when he showod that light moved slower in water than
in air.
 contributed to the development of the ether theory. However, we now know
that ether does not exist-it was proved conclusively by Albert Abraham
Michelson (1832-1931) and Edward Williams Morley (1838-1923) in 1887.
Poisson (1781-1840), Cauchy (1789-1857) and several other physicists

Heinrich Herts (1857-1894)
 provided a direct evidence for the existence of electromagnetic
waves in 1888 through series of brilliant experiments.
 In 1887, Hertz had made a very striking discovery-the photoelectric effect.
He observed that when a metal surface was irradiated by light of frequency
above a certain critical value ,it ejected electron. This phenomenon could not
he explained on the bans of wave theory of ligh became kinetic energy of an
ejected electron was seen to be independent of the intensity of light.

Albert Einstein (1879-1955)
 German-Swiss physicist, interpreted the photoelectric effect using
the concept of quantum thoory developed by German theoretical
physicist Max Planck (1858-1947) for blackbody radiation.
 In his theory of blackbody radiation, Planck discarded classical theories and
postulated that energy was omitted or absorbed by an individual resonator in
quanta' of magnitude Einstein proposed that rather than a wave, light also
behaved as a "discrete quanta” or “particle localized in space”
 (We may mention that the word photon was coined by Gilbert N. Lewis in 1926
to describe Einstein's discrete quanta").
Max Planck (1858-1947)

 Wave and Particle concepts provided physical basis for the work of
Neils Bhor and Arthur Compton on scaterring of X-rays from
electrons as particle collisions between photons and electrons.
 These developments suggested that light could be treated as a particular kind
of matter, possessing both energy and momentum leading to what is now
known as wave-particle duality: Light behaves like waves when it propagates in
a medium or exhibits the phenomena of interference and diffraction. Light also
behaves as particles in its interaction with matter, as in the photoelectric effect.

The way to get
started is to quit
talking and begin
doing.
Walt Disney

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