1. The Nature of
Light
The Electro
The Dual
Magnetic
Nature of Light
Spectrum
Luminous and Opaque,
Different
Illuminated Transparent
Sources of Light
Objects and Translucent

2. The Dual Nature of
Light
Light Light
as a as a
wave particle

3. The WAVE Theory of
Light The theory that lights is transmitted
via wave form was proposed by
Christian Huygens in 1679. According to
•light corpuscles have mass and travel at extremely
the theory:
high speeds in straight lines
•rectilinear propagation - blocked by large objects
(well-defined shadows)
•obey the law of reflection when bounced off a
surface
•speed up when they enter denser media

4. The Particle Theory
of Light transmitted via corpuscar
The theory that light is
form was supported and
•wavelet envelop model (each point onIsaac Newton.
advocated by Sir a wavefront
According to his theory:
acts as a source for the next wavefront)
•plane waves generate plane waves, circular waves
generate circular waves
•light was composed of longitudinal waves like
sound
•obey the law of reflection when bounced off a
surface

5. The
Electromagnetic
Spectrum
The electromagnetic spectrum is the range of all possible
frequencies of electromagnetic radiation. Electromagnetic
waves are formed when an electric field couples with a
magnetic field. It is a continuum of all electromagnetic waves
arranged according to frequency, wavelength and energy.

6. frequency, wavelength and
energy
• Wavelength is inversely proportional to the wave
frequency
• Photon energy is directly proportional to the wave
frequency
λ=E/f

8. Electromagnetic Spectrum:
Radio Infrared
Microwaves
Waves Radiation
Visible Light Ultraviolet
X-rays
(Light) Light
Gamma
Rays

9. RMIVUXG =
Rattlesnakes May
Inject Venum Under
Xtreme aGitation 

10. Radio waves Microwaves
•Have the longest •Very easily absorbed by water
wavelengths but least
energetic •Cause water and fat molecules to
vibrate, which makes the
substances hot.
•Utilized by antennas
•Good for transmitting information
•They are used for
because microwave energy can
transmission of data, via penetrate haze, light rain and
modulation. snow, clouds, and smoke.
•Television, mobile phones, •Mobile phones, fixed traffic speed
wireless networking, and cameras, and radar, which is used
amateur radio all use radio by aircraft, ships and weather
waves. forcasters, all use microwaves.

11. Infrared Light
Radiation Visible light waves are the only
•Can be detected by special electromagnetic waves we can
infra-red film.
see. We see these waves as the
•Primary source of infrared colors of the rainbow.
radiation is heat or thermal
radiation
•Our skin emits infrared light,
which is why we can be seen in
the dark by someone using
night vision goggles.
•Ex. remote control

12. UV rays X-rays
•Main natural source is the sun •Also called as Roentgen rays
and other stars in honor of their discoverer
•Can break chemical bonds, •Given off by stars and are
making molecules unusually strongly emitted by some
reactive types of nebulae.
•Often harmful to plants and •Have so much energy and
animals, including humans such a short wavelength that
they can go right through you
•Used to kill microbes, getting • Used by doctors to see
a sun tan, detecting forged inside people
bank notes

13. Gamma Rays
•Shortest-wavelength, Highest energy
•Most dangerous and most penetrating of
all electromagnetic radiation, and are
quite difficult to stop
•Result of violent cosmic events such as
supernovas, other nuclear explosions, and
radioactive decay
•Used to kill cancer cells ("Radiotherapy")

14. Light
Sources
Light is a form of energy. To create light, another form of
energy must be supplied. There are two common ways
for this to occur, incandescence and luminescence.

15. "Black body radiation"
It is the emission of light from a hot
body as a result of its temperature.
Incandescence Involves the vibration of entire atoms
Sunlight, regular light bulbs (not
florescent) and fires are all
incandescent sources of light.
"Cold light"
It is the emission of light by a substance
not resulting from heat. It can be caused
by chemical reactions, electrical energy,
subatomic motions, or stress on a crystal.
Luminescence
Involves only the vibration of electrons
Ex. computer monitors, televisions, and
florescent lights, fireflies

16. Luminous and
Illuminated Bodies
The objects that we see can be placed into one of two categories:
luminous objects and illuminated objects. Luminous objects are
objects that generate their own light. Illuminated objects are
objects that are capable of reflecting light to our eyes.

17. A luminous body, such as the sun, another star,
or a light bulb, is thus distinguished from an
illuminated body, such as the moon and most
of the other objects one sees. Luminous objects
give off light whereas illuminated objects
relfect light. Examples of luminous bodies are
the sun, stars, fireflies, lighted candle, light
Illuminated bodies not only
bulbs..
reflect light but sometimes also
transmit it, such as the opaque,
transparent and translucent

18. Opaque,
Translucent or
Transparent?

19. Water

20. Plastic
Bags

21. Wind

22. Wood

23. Tissue
Paper

24. Books

25. c
Glass

26. Translucent Transparent
Objects Objects
•These kinds of objects scatter or
disperse light when light falls on •They are those that allow
them. light to pass through readily.
•They are said to transmit light in •These kind of objects have
the absence of details absolute clarity.
•You can only see a blur image •You can see right through
when you peek through these them.
•Frosted glass and waxed paper •The water, air and glass are
are examples of translucent all transparent objects.
objects.

27. Opaque
Objects
•These objects do not allow light to pass through.
•They absorb some of the light that is cast on
them.
•Wood, paper and many more are examples of
such objects.