The document discusses the history and theories of light, including: 1) Christian Huygens' wave theory from 1690 which considered light a wave. 2) Isaac Newton's particle theory from 1704 which considered light particles. 3) James Clerk Maxwell's electromagnetic theory from 1860 which considered light an electromagnetic wave. 4) Max Planck's quantum theory from 1900 which considered light emitted in quanta called photons. The document also discusses the dual nature of light as both a particle and wave.

1. Optics
Theories
Wave-Particle Duality
Propagation
Wave Speed
Luminosity
Illumination

2. The Theories of Light
1. Wave Theory
• proposed by Christian Huygens in 1690
• considers light to be a wave
propagating in ether (an assumed
substance permeating all matter and
space
2. Corpuscular or Particle Theory
• proposed by Isaac Newton in 1704
• considers light as composed of tiny
particles emitted by luminous object
• cited formation of shadows as proof

3. The Theories of Light
3. Electromagnetic Theory
• proposed by James Clerk Maxwell in
1860
• considers light as an electromagnetic
(EM) wave, a transverse wave that is
partly electrical and partly magnetic in
nature
4. Quantum Theory
• proposed by Max Planck in 1900s
• considers light as being emitted by
packets of energy called quanta
• Einstein called each quantum of
energy as photon

4. The Dual Nature of Light:
A PARTICLE AND A WAVE
• Since light has a dual nature, then it has two models or it
can be presented and analyzed in two ways: as a ray
and as a wave.
• Ray Model of light is used to describe light as a particle
and its behavior as a particle, and such is under the
study of GEOMETRIC / RAY OPTICS.
• Wave Model of light is used to describe light as a wave
and its behavior as a wave, and such is under the study
of WAVE OPTICS.

5. Measuring the Speed of Light
1.
2.
3.
4.
5.
Olaus Roemer – 300 000 000 m/s
Christian Huygens – 230 000 000 m/s
Armand Louis Fizeau – 313 000 000 m/s
Jean Bernard Leon Foucault – 299 796 000 m/s
Albert Michelson – 299 799 600 m/s
Accepted Value:
299 792 458 m/s ~ 300 000 000 m/s

6. The Rectilinear Propagation of Light
RECTILINEAR PROPAGATION
- property of light to travel in a straight path
- one evidence of rectilinear propagation of light
is the creation of a shadow

7. When can we see objects?
1. Luminous Object –
object that can
generate its own light
2. Illuminated Object –
object that can not
generate its own light
but can still be seen
because it can reflect
light that it received
from other sources

8. Types of Luminosity
1. Incandescence – emits light due to their
hot bodies.

9. Types of Luminosity
2. Fluorescence – emits light by utilizing
phosphors, which absorbs ultraviolet energy
and releases visible light.

10. Types of Luminosity
3. Phosphorescence – a type of
fluorescence where the emission of light
persists even after external excitation.

11. Types of Luminosity
4. Gas Discharge – some gases can be
made to produce light by passing an electric
current through them.

12. Types of Luminosity
5. Bioluminescence – light produced in
living organisms through chemical reactions
between protein and oxygen.

13. MEASURING LIGHT
Luminous Intensity (I)
– strength or brightness of a source of light;
measured in candela (cd)
Luminous Flux (F)
– rate at which light is emitted from a source and
strikes the surface of a whole sphere; measured
in lumens (lm)
Illumination (E)
– the amount of luminous flux falling on a unit
area of a surface; measured in lux (lx)

14. Illumination and Distance:
THE INVERSE SQUARE LAW
• Illumination of light is inversely proportional to
the square of the distance from the source
• This means that the farther an object is from a
light source, the lesser light falls on it.
Examples:
• If you move 2× away from a light source, you’ll
receive only 1/4 of the original illuminance.
• If you move 3× away from a light source, you’ll
receive only 1/9 of the original illuminance.