Light is a transverse, electromagnetic wave that can be seen by humans. The wave nature of light was first illustrated through experiments on diffraction and interference. Like all electromagnetic waves, light can travel through a vacuum. The transverse nature of light can be demonstrated through polarization.

1. Light
By Prof. Liwayway Memije-Cruz

2. Concepts of Light
Light is a transverse,
electromagnetic wave that
can be seen by humans. The
wave nature of light was
first illustrated through
experiments on diffraction
and interference. Like all
electromagnetic waves,
light can travel through a
vacuum. The transverse
nature of light can be
demonstrated through
polarization.

3. Properties of Light

4. Properties of Light
Light is a form of energy. When something burns it often gives off light
energy as well as heat energy. The sun, for example, is a ball of burning
gases which give off lots of light. The earliest form of light that humans
used was the light created from burning wood. Today we get light from
many different sources both natural and artificial.
Light travels in waves (light waves) like ripples across a pond. The waves
all travel through air at the same speed (300 000 kilometers per second,
the fastest speed there is). The light from the sun, which is approximately
150 million kilometers away, can reach the Earth in about eight minutes.
Light waves usually travel in straight lines called rays of light. Each light
wave is made up of different wavelengths which make different colours
of light. Light waves may be reflected (bounce off) or refracted (change
direction) and may change speed depending on the material they are
passing through.

6. Reflection of Light
it reflects off surfaces.
Among other things, this
reflection allows us to see
images in mirrors. We see
the images in mirrors as
apparently coming from
behind the mirror because
our eyes interpret it in this
manner. But when we see
ourselves reflected in the
mirror and raise our left
arm, the image apparently
raises its right arm.

7. Speed of Light
 the fastest anything has been
observed to move.
 In a vacuum, the speed is 300 million
meters per second. At that speed, it
takes light one ten thousandth of a
second to travel around the earth.
 When light enters a material, it
slows down. The amount depends on
the material it enters and it’s density.
For example, light travels about 30%
slower in water than it does in a
vacuum, while in diamonds, which is
about the most dense material, it
travels at about half the speed it does
in a vacuum. This slowing down of
light plays a role in another property,
refraction.

9. Refraction
Refraction means that light
bends when it passes from
one medium to another.
When light enters a denser
medium from one that is less
dense, it bends toward a line
normal to the boundary
between the two media. The
greater the density difference
between the two media, the
more the light bends. This
property is used with respect
to optical devices such as
microscopes, corrective
lenses for vision, magnifying
lenses, and so on.

10. Refraction
when you look into the surface
of a lake or pond while fishing,
the fish you catch seems larger
when under the water than
when you actually land it. This
is due to refraction. Since the air
is less dense than water, the
light beds away from the normal
as it emerges. Another common
example is that your feel look
larger and closer to the surface
underwater than they really are

11. Interference and diffraction
Interference and diffraction are terms that describe a wave
interacting with something that changes its amplitude, such as
another wave.

12. Interference is a phenomenon in which two waves
superimpose to form a resultant wave of greater or
lower amplitude.
 Constructive interference occurs when the phase
difference between the waves is a multiple of 2π,
whereas destructive interference occurs when the
difference is π, 3π, 5π, etc.
Diffraction refers to various phenomena that occur
when a wave encounters an obstacle. In classical
physics, the diffraction phenomenon is described as the
apparent bending of waves around small obstacles and
the spreading out of waves past small openings.

13. Diffraction
refers to various phenomena
that occur when a wave
encounters an obstacle. In
classical physics, the
diffraction phenomenon is
described as the apparent
bending of waves around
small obstacles and the
spreading out of waves past
small openings.

14. Electromagnetic waves
Like all electromagnetic waves, light can travel through a
vacuum. The transverse nature of light can be demonstrated
through polarization.

15. Polarization and Polaroid Filter
The process of transforming unpolarized light into polarized light is
known as polarization.
he most common method of polarization involves the use of a
Polaroid filter.
Polaroid filters are made of a special material that is capable of
blocking one of the two planes of vibration of an electromagnetic
wave.

16. Sources of Light

17. Sun: Natural Light
 Our main source of natural light is
the sun. The sun is a star that is a
huge ball of gas. Explosions at the
centre of the sun produce large
amounts of energy. This energy is
released as light and heat. Some of
this light reaches Earth and gives us
daylight. The light that comes from
the sun is known as white light.
 Other forms of natural light include
the moon and the stars. The stars
provide only small amounts of light
at night as they are billions of
kilometers away from Earth. A full
moon, however, can provide quite a
lot of light. The light from the
moon is just light reflected from the
sun.

18. Bioluminescence
Some animals can produce
their own light known as
bioluminescence. A
chemical reaction is
produced in special light-
producing cells. This light
is then used in a variety of
ways but mainly to attract
other creatures. Glow-
worms, fireflies, some fish
and mushrooms are
examples of living things
that can create their own
light.

19. Artificial Light
Humans have been able to
create and control light for
thousands of years.
The earliest form of lighting
was with fire such as burning
wood, candles, gas or oil.
Candles were made out of
beeswax or tallow (animal
fat).
Oil lamps used plant or
animal oil and a wick to
burn.
 electric light - the most
convenient source of
artificial light .

20. Measurement of Light

22. Lens
a carefully ground or
molded piece of
transparent material that
refracts light rays in such as
way as to form an image.
a series of tiny refracting
prisms, each of which
refracts light to produce
their own image. When
these prisms act together,
they produce a bright
image focused at a point.

23. Types of Lenses
A converging lens is a lens
that converges rays of light that
are traveling parallel to its
principal axis. Converging
lenses can be identified by their
shape; they are relatively thick
across their middle and thin at
their upper and lower edges.
A diverging lens is a lens that
diverges rays of light that are
traveling parallel to its principal
axis. Diverging lenses can also
be identified by their shape; they
are relatively thin across their
middle and thick at their upper
and lower edges.

24. Optical Instruments
Optical instruments are
the devices which processes
light wave to enhance an
image for more clear view.
You use an optical
instrument usually to make
things bigger and to see fine
details of objects with the help
of something very simple like
a magnifying glass or any
complicated device like
microscope or telescope.

26. References
http://www.physicsplanet.com/articles/properties-of-light
http://www.physicsclassroom.com/class/refrn/Lesson-
5/The-Anatomy-of-a-Lens
https://www.pinterest.com/mccarthyarch/color-
psychology/