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Concave and Convex Mirrors

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Stephanie Athayde

on 21 April 2014

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Transcript of Concave and Convex Mirrors

Optics
Types of Light Sources
Incandescence
process of emitting light because of high temperatures.
an incandescent light bulb has a tiny tungsten wire that gets very
hot
and glows when electric current runs through it
inefficient at
producing
light
5% light efficiency
95% lost as heat

Opacity
Transparent
objects let all light pass through.
Translucent
objects
let some light pass through.
Opaque
objects let no light pass through.

Light is
not
a form of matter.
Light
Visible Spectrum
Red has the

longest

wave length, and

lowest frequency
Purple has the

shortest

wave length,
and

highest frequency



Wave lengths
are the distance between two adjacent crests, or troughs of a wave.

The

amplitude
refers to the distance from the midpoint of the wave to its crest, or trough.

Frequency
is the number of wave lengths in a
period of time
.

Luminosity
Luminous
objects
emit
energy in the form of light.
Non luminous
objects do not emit light, but
reflect
it from other sources.
Uses of Fluorescence
forensic scientists use
ultraviolet lights
at crime scenes to find blood, urine and semen
many
body fluids
contain fluorescent molecules
Types of Curved Mirrors

Concave (converging) mirrors
Some
optical devices
that make use of concave mirrors are:


Eye
Anatomy
Sclera
is the tough, white outer layer of the eyeball.
Cornea
is the transparent front part of the eye that helps focus light.
Iris
is the colorful ring of muscle that monitor light entering pupil.
Pupil
dilates, or constricts by the iris so light enters the lens, acting as the"window" of the eye.
Lens
focuses light on the retina.
Ciliary muscle
holds the lens in place, and makes it thicker for near objects, and thinner for far objects.
Retina
is light sensitive, so this is where the image is produced.
Optic
nerve carries the signal to the brain.
Photoreceptor Cells
Cones
in the retina are sensitive to primary colors; there are approximately 7 million of them.
Rods
in the retina are sensitive to shades; there are approximately 120 million of them.
Vision Problems
Myopia is commonly known as nearsightedness
Hyperopia is commonly known as farsightedness
Astigmatism is the condition where the cornea has an irregular curvature which makes for blurry vision
Presbyopia is the condition which causes the inability to focus on either nearby or far away objects
Colors
Primary colors our eyes can detect.
Secondary colors are results from mixing any two primary colors.
Complementary colors are any two colors of that produce white light when added together

it doesn't have

mass

or take up

space
Did you know?
Some Ancient Greek philosophers believed that light travels from our eyes to the objects we look at, rather than from the objects to our eyes.
Light and the Wave Model
Light energy travels in a wave that is
partly electric
and
partly magnetic.
Such a wave is called an
electromagnetic wave
.

electromagnetic waves can travel through a vacuum at the speed of light:
The

highest points

of a wave are called
crests

The

lowest points

are called
troughs

in a fluorescent bulb, the excited
Hg
atoms emit excess energy in a form of ultraviolet light
the energy of the ultraviolet light excites atoms in the phosphor lining of the tube and emits visible light
20% light efficiency
Hg – hazardous waste

1. Fluorescence
Luminescence
light that is generated
without
heating an object

Types of Luminescence:
1. Fluorescence
2. Phosphorescence
3. Chemiluminescence
4. Bioluminescence

light that is emitted during exposure of the source to
ultraviolet light

R
abbits
M
ate
I
n
V
ery
e
X
pensive
U
nusual
G
ardens
2. Phosphorescence
Phosphorescence process of

emitting

light for a
short time after

receiving energy from another source
.
(glow in the dark)

3. Chemiluminescence
process of changing
chemical energy
into light energy with little or no change in
temperature
. (
glow stick
)
4. Bioluminescence
any process used by
living things
to transform
chemical
energy into light energy

By the end of today's class you will be able to:

• describe the properties of light
• explain the visual colour spectrum using the wave model of light
• identify the different wavelengths of the electromagnetic spectrum
• identify different sources of light

Exit Card 3-2-1
On a piece of paper:

1.
List
and
describe
3 things you found interesting from todays lesson

2. Name
2 occupations
that use properties of optics (from todays class)

3. Create/ recall a
mnemonic
that helps you to remember the
visible light spectrum

Ray Model of Light
By the end of today's class you will be able to:
• learn how light is reflected from two different types of curved mirrors
• locate images produced by these two different mirrors
• investigate the characteristics of the different images produced


All mirrors, plane or curved, follow the
Law of Reflection
The
reflection position

of light rays hitting their surfaces is the main
difference
between a plane mirror and a curved mirror














Umbra

is the darkest part of the shadow, no light from source is reaches there.

Penumbra

is the lighter part of the shadow, some light from the source reaches there.
Concave Mirrors
Concave mirrors are also called
converging
mirrors because when incident rays of light hit the surface of a concave mirror, the reflected rays converge to one point in front of the mirror.


The images formed by curved mirrors depend on where the object is placed from the
focal point


flashlights
telescopes
headlights

Convex Mirrors
The
big difference
between concave and convex mirrors is in the location of the

focal point (F)
centre of curvature (C)


The funny images that you see in a
house of mirrors
at a fun house or carnival use the principles of
geometric optics
. These mirrors are produced to have multiple curves and have no practical applications outside of the carnival fun house.
reversed
upright
same size

convex (diverging) mirrors
.
Where else can the object be?


these devices are designed to
collect
light and bring it to a
single

point
Convex mirrors are also called
diverging
mirrors because when parallel rays hit the surface of this type of mirror, the reflected rays diverge from a single point
behind
the mirror.
The
focal point
of
convex
mirrors is located
behind
the mirror

Likewise, the
centre of curvature
is also located
behind
the mirror in
virtual space
Some

optical devices
that make use of

convex
mirrors are:
mirrors used by mechanics
side-view mirrors in cars
security mirrors
Calculating Magnification
The image formed by a concave or convex mirror or lens can be described based on its
characteristics
Characteristics of an Image
1. Location
closer than, farther than, or the same distance as the object to the mirror
2. Orientation
upright or inverted
3. Size
same size, larger than, or smaller than the object
4. Type
real or virtual image

L.O.S.T.
How do you draw a normal on a curved surface?
think of the curved surface as many small, flat mirrors

centre of curvature (C)
– all the normals meet at this point

principal axis
– the line that passes through the centre of curvature (C) and is normal to the centre of the mirror

vertex (V)
– the point at which the principal axis cuts the centre of the mirror

Incident Ray Passes Through the Centre of Curvature
think of the curved surface as many small, flat mirrors

the incident ray passes right over the normal
the angle of incidence and the angle of reflection are zero

Incident Ray is
Near
and
Parallel
to the Principal Axis
focal point (F)
– the point on the principal axis through which reflected rays pass when the incident rays are parallel to and near the principal axis

focal length (f)
– distance between the vertex (V) and focal point (F)


Rules
1. All rays that are parallel to the principal axis will reflect through F

(if it goes parallel – it reflects through F)

2. All rays that are incident through F will reflect parallel to the principal axis
(if it goes through F – it reflects parallel)

3. All rays that are incident through C will reflect through C
(if it goes through C – it reflects through C)

Ray Diagrams for 3 Possibilities

Object between F and a Concave Mirror
(if it goes parallel – it reflects through F)
(if it goes through F – it reflects parallel)


(if it goes through C – it reflects through C)
Object between F and a Concave Mirror
Object between F and a Concave Mirror
Object between F and a Concave Mirror
Object between F and a Concave Mirror
Object between F and a Concave Mirror
1. Location
the image distance is
greater
than the object distance
2. Orientation
the image is
upright
3. Size
the image is
larger
than the object
4. Type
the image is
virtual

L.O.S.T.
Object between F
and
C in Front of a Concave Mirror
1. Location
the image distance is
greater
than the object distance
2. Orientation
the image is
inverted
3. Size
the image is
larger
than the object
4. Type
the image is
real

L.O.S.T.
Object between F
and
C in Front of a Concave Mirror
Object between F
and
C in Front of a Concave Mirror
Object between F
and
C in Front of a Concave Mirror
Object between F
and
C in Front of a Concave Mirror
Object between F
and
C in Front of a Concave Mirror
real image

– an image that is formed when reflected rays meet
– forms a visible projection on a screen

Object
beyond
C in Front of a Concave Mirror
1. Location
the image distance is
smaller
than the object distance
2. Orientation
the image is
inverted
3. Size
the image is
smaller
than the object
4. Type
the image is
real

L.O.S.T.
Object
beyond
C in Front of a Concave Mirror
Object
beyond
C in Front of a Concave Mirror
Object
beyond
C in Front of a Concave Mirror
Object
beyond
C in Front of a Concave Mirror
Object
beyond
C in Front of a Concave Mirror
Drawing a Ray Diagram for a Convex Mirror
1. Location
the image distance is
smaller
than the object distance
2. Orientation
the image is
upright
3. Size
the image is
smaller
than the object
4. Type
the image is
virtual

L.O.S.T.
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