OPTICS
What is light?
Light is a form of energy that can be detected by the
human eye.
What is natural light source?
The Sun is a natural light source, the most
abundant and least expensive light source in the
world
What is a radiant?
A radiant is energy that is sent out in the
form of waves or rays.
What is radiation?
Radiation is the heat
transfer of radiant energy
waves or rays such as light.
•wavelength (color, frequency) corresponds to the
energy of the light
What is radiant energy?
Radiant energy is energy
transferred or emitted as
waves or rays in all
directions.
What is an artificial light source?
An artificial light source is a human
made source of light.
What is illumination?
The amount of light cast on a subject.
What is the main source of
illumination on Earth?
The Sun is the main source of illumination on Earth.
What is artificial illumination?
Artificial illumination is light energy that is man made so
humans could see in the dark.
Where does light energy come
from?
Light energy comes form two different sources, natural and
artificial.
What is the most important
source for natural light?
The sun is the most important source for natural
light.
What are luminous objects?
Luminous objects are objects that give off their own
light.
What are nonluminous objects?
Nonluminous objects are objects that do not give off light.
Why is the Moon nonluminous?
The Moon is nonluminous because it reflects light from the Sun
What are some common forms of
luminous energy?
Some common forms of energy are:
Chemical energy
Electrical energy
Nuclear energy
Thermal energy
What does incandescence mean?
Incandescence means the release of visible
light by a hot object.
What does phosphorescence mean?
Phosphorescence is the process of giving off light
for sometime after receiving light from another
source.
What is fluorescence?
The release of light from a substance caused by
exposure to radiation from an external source
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Where are fluorescent lights used?
Fluorescent lights are used in:
Schools
Offices
Homes
What is Chemiluminescence ?
Chemiluminescene is the process of changing
chemical energy into light energy with little or no
change in temperature.
A chemical reaction that gives off energy in the form
of light instead of heat. We all love glow sticks,
which illustrates this process perfectly. When a glow
stick is bent, a glass vile inside releases the
chemicals and produce light.
What is Bioluminescence?
Bioluminescence is any process used by living things to
transform chemical energy into light energy.
Give examples of bioluminescence.
Firefly
Zebra Fish
Hawaiian bobtail squid
Glow
worm
Bacteria
Fungi (mushrooms)
Daytime
Nighttime
Which of the following are
luminous?
A. Campfire
B. The Moon
C. A hot toaster filament
The campfire and hot toaster are
luminous.
WHY?
For, luminous objects are objects that
give off their own light.
Explain in your own words the difference
between a phosphorescent source and a
fluorescent source.
The main difference is that a fluorescent source emits light
only while it is receiving energy from elsewhere, but a
phosphorescent source can continue to emit light for some
time after the source of energy is removed.
Describe how it can also be
nonluminous.
The flashlight can be nonluminous when it is turned off.
What is a dark and light shadow?
A shadow is formed where light is 'missing'. A dark
shadow (umbra) is formed where no light falls and
a light shadow (penumbra) is formed where some
light falls, but some is blocked.
If the light source is very tiny and concentrated in
one place (a point source) only a sharp shadow is
formed.
If the source is broader light from the top of the
source causes a lower shadow than that from the
top. You therefore get partial shadow or
penumbra as well as umbra.
If we use coloured lights at different points we can see
the effect of these multiple shadows:
The size of a shadow
changes as you move the
source closer or further from
the screen
As you move the object closer or further from the
screen.
What is reflection?
Reflection occurs when a ray of light is returned
after hitting a surface.
What is an incident ray?
An incident ray is a
light ray that strikes a
surface. When light
strikes a reflecting
surface, it bounces off
the surface.
What is a reflected ray?
A reflected ray
is the light that
is reflected
from a surface.
To find out in which direction each ray of light is
traveling, you can measure an angle.
To do this, draw a reference line that is
perpendicular (90 degrees) to the reflecting surface
at the point where the incident ray strikes the
surface.
This line is called normal (definition-reference
line that is perpendicular - 90 degrees- to the
reflecting surface).
The angle between the incident ray and the normal is
called the angle of incidence, i.
The angle between the normal and the reflected
ray is called angle of reflection, r.
Two laws of reflection?
1.
The angle of reflection, r, is always equal to the
angle of incidence, i.
2.
The incident ray, the normal, and the
reflected ray are always in the same plane.
What happens to light when it
reflects off a rough surface?
When light reflects off a rough surface the light reflects
in all directions, so very little light will defect.
What is transparency?
Transparency is a measure of how much light can pass
through a material.
A shadow results because light travels in
straight lines from its source and does not
bend around objects
How are materials classified?
Materials(matter) are
classified as transparent,
translucent and opaque.
Describe transparent and give an example.
Transparent: The ability to see through an item. Allowing
light to pass through so that objects may be clearly seen.
The opposite of transparent is opaque.
Example: Plastic wrap
Describe translucent and give an example.
Translucent: Allowing some
light to pass through an object
without seeing clearly
through the object.
Example: skin, frosted
glass and clouds
Flesh is transparent to X-rays,
while bone is not, allowing the
use of medical X-ray machines.
Describe opaque and give an example.
Substances that allow no light through them. Opaque means
not see-through. Not allowing light to pass through, it is the
opposite of transparent.
Examples: milk, wood, stone and brick
Light will travel in straight lines until it strikes
something.
When does reflection occur?
Reflection occurs when a ray of light is returned after
hitting a surface.
Are the following transparent, translucent or opaque?
A.
Very Smoky Air
B.
Waxed paper
C.
A copper plate
D.
An ice cube
What happens when a beam of light strikes a
rough or irregular surface?
The angle which light strikes and reflects will be equal at
each point of the angle, but the surface has many different
directions and therefore so will the reflected rays. As a
result, a rough surface will be visible from almost any
position.
In contrast, to see light from a mirror, the eye must be
looking in the direction in which the angle beam is
reflected.
What is
reflected light?
It is the concept that all
objects reflect light: some
more than others. It is this
reflected light that enters
the eye and enables us to see
the object such as surface
texture, colour dimensions.
What is regular reflection?
The reflection of light off a smooth, shiny
surface.
Law’s of Reflection
There are three laws of reflection that describe the
reflection from plane mirrors:
1. The angle between the incident ray and the normal is
equal to the angle between the reflected ray and the
normal.
2. The incident ray, the normal, and the reflected ray are
all in the same plane.
3. Incident ray and reflected ray are on different sides of
the normal
1. The angle between the incident ray and the
normal is equal to the angle between the reflected
ray and the normal.
2.
The incident ray, the normal, and the reflected ray
are all in the same plane.
3.
Incident ray and reflected ray are on different sides of
the normal
You can improve your pool game by applying the
laws of reflection.
What is diffuse reflection?
When light hits an irregular surface reflected light
scatters in many directions.
Why is diffuse light easier on your eyes than
other types of reflected light?
Diffuse light is easier on your eyes because it’s light is
reflected and scattered in many directions. Direct light
and glare strain your eyes. Diffusion allows you to see
object with ease. Diffusion is found in homes, schools
and places of work.
Describe regular reflection and diffuse
reflection.
Regular reflection is the reflection of light off a smooth, shiny,
regular surface.
In diffuse reflection, light is reflected off an
irregular surface in many directions.
What are plane mirrors?
Plane mirrors are regular flat mirrors.
What is refraction?
The action of changing the direction of a light wave,
so the light enters the object in one direction, and
leaves it in another.
Looks like a broken pencil
What happens to the light ray when it passes
through air and glass?
If a light ray passes form a less dense substance such
as air into a denser substance such as glass, it will
bend towards the normal.
What happens when a light passes from a
denser to a less dense material?
When light passes form a denser to a less dense
material, it will bend away from the normal. The
amount of refraction depends on the angle of the
incoming ray
What happens when a light wave
impacts another material at right
angles to its surface?
Light waves that impact another material at right
angles to its surface do not bend because each point
on the wave front reaches the boundary at the same
time. The light ray is approaching the boundary
traveling along the normal.
If the block has parallel sides (as in my sketch)
the ray comes out of the block at the same
angle as it entered,
Why do birds diving do fish usually enter the
water at right angles?
Birds dive at right angles perpendicular to the
water’s surface so their vision is not distorted.
You can see why birds dive at right angles.
If not their vision get distorted and they
are not successful at catching their food.
This is how the archer fish positions itself for
food. The key to food is to travel along the
normal.