23-SNC2P-Topic_4

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Topic Concave Mirrors Can Form Real
4.4 Inverted Images.
(Pages 314-317)
TODAY WE WILL...
 Have a quick review about plane mirrors, and the
terms of a concave mirror.
 Practice the steps to draw the images in concave
mirrors.
 Complete all three scenarios for images in concave
mirrors.
SUCCESS CRITERIA
- You will be successful if you can draw the images of the
objects for all three concave mirror scenarios.
LET’S REVIEW ...
 LAST WEEK WE COVERED ...
 LAWS OF REFLECTION
 IMAGES IN PLANE MIRRORS
 THIS WEEK WE COVERED ...
 CONCAVE MIRRORS
The angle of reflection is equal to
the angle of incidence.
Copyright © 2010 McGraw-Hill Ryerson Ltd.
The Law of Reflection
The Law of Reflection applies to every reflecting surface. The word
“plane” refers to any flat surface.
Copyright © 2010 McGraw-Hill Ryerson Ltd.
WHAT IS AN IMAGE?
When you see an object reflected in a mirror, you
do not see the object itself.
Instead, you see an IMAGE of the object.
IMAGE: a picture or reproduction of an object
formed using light.
Ray Diagrams for Plane Mirrors
You need just two rays reflecting from a mirror to find the point
where the reflection of an object is located.
The virtual image is an image located
where no light rays ever meet. Rays
must be extended behind the mirror
to find where they meet.
• OBJECT: the item in front of the
mirror
• IMAGE: the reflection of the object
in the mirror
• OBJECT DISTANCE: the distance
from the mirror to the object
• IMAGE DISTANCE: the distance
from the mirror to the image.
Copyright © 2010 McGraw-Hill Ryerson Ltd.
CHARACTERISTICS OF IMAGES
IN A PLANE MIRROR
Describe the image characteristics for an image in a plane
(flat) mirror.
SIZE:
Same size as the object.
ATTITUDE: Upright ... Image is oriented in the same direction as
the object.
LOCATION: Image is behind the mirror, and the image distance is
equal to the object distance.
TYPE:
The image is virtual.
Curved Mirrors
There are two types of
curved mirrors:
 Concave (converging)
 Convex (diverging)
Concave Mirrors
Vertex (V)
Principle
Axis (PA)
Centre of
Curvature (C)
Focal length (f)
Focus (F)
2 times the focal length
(2f)
Concave mirrors ... terms
PRINCIPAL AXIS (PA): a straight line that passes through the
centre of curvature, C, to the midpoint of the mirror
VERTEX (V): the point where the principal axis meets the mirror
FOCAL POINT [or focus] (F): the point where all light rays that are
parallel and close to the principal axis
reflect from the mirror and meet
CENTRE OF CURVATURE (C): the centre of the sphere that the
mirror fits on. The focal point is exactly
halfway between C and the mirror.
RADIUS OF CURVATURE: the distance between C and V
FOCAL LENGTH (f): the distance from the focal point to the mirror
WORKSHEET 4.4C
Images in curved mirrors have 4 key characteristics:
 SIZE
• Is the image larger, smaller, or the same size compared to the
object?
 ATTITUDE
• Is the image upright (right side up) or inverted (upside down)?
 LOCATION
• Where is the image located?
 TYPE
• Is the image real or virtual?
RECALL ... Ray Diagrams for Concave Mirrors
There are three regions where an object can be located:
•beyond C
•between C and F
•between the mirror and F
Locating Images in Concave Mirrors
 To find the image of an object in front of a
concave mirror, you need to draw at least two
incident rays from the top of the object.
RULES:
1. The first ray is drawn
parallel to the principal axis,
and it will reflect back
through the focal point.
Locating Images in Concave Mirrors
RULES ... Cont’d:
2. The second ray is drawn
from a point on the object
through the focal point
toward the mirror, and it will
reflect back, parallel to the
principal axis.
Ray Diagrams for Objects between
F and C for Concave Mirrors
Pg.314
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Ray Diagrams for Objects between
F and C for Concave Mirrors
Pg.314
The 4 characteristics of the image of an object placed
between F and C of a concave mirror are:
• S: the image is larger than the object
• A: the image is inverted
• L: the image is farther from the mirror than the object
• T: the image is real
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Ray Diagrams for Concave Mirrors
The three regions where an object can be located:
•beyond C
between C and F
•between the mirror and F
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Concave mirrors can form upright,
virtual images.
The image below shows how concave mirrors can form
magnified, upright images, much like a makeup mirror does.
For this to occur the object must be between the mirror and
the focal point (F). If not, the image is inverted.
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Ray Diagrams for an Object between a
Concave Mirror and the Focal Point
Pg.317
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Ray Diagrams for an Object between a
Concave Mirror and the Focal Point
Pg.317
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Ray Diagrams for an Object between a
Concave Mirror and the Focal Point
Pg.317
The 4 characteristics of the image of an object placed
between F and the concave mirror are:
• S: the image is larger than the object
• A: the image is upright
• L: the image is farther from the mirror than the object
• T: the image is virtual
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Ray Diagrams for Concave Mirrors
The three regions where an object can be located:
•beyond C
between C and F
between the mirror and F
Ray Diagrams for an
Object beyond C
Use the same directions on page 314 (Object between C
and F) to draw the ray diagram.
1. The first ray is drawn parallel to
the principal axis, and it will
reflect back through the focal
point.
2. The second ray is drawn from a
point on the object through the
focal point toward the mirror,
and it will reflect back, parallel
to the principal axis.
Ray Diagram for an object located beyond C
The 4 characteristics of the image of an object placed
beyond C are:
• S: the image is smaller than the object
• A: the image is inverted
• L: the image is located between C and F
• T: the image is real
SUMMARY: IMAGE CHARACTERISTICS
OF A CONCAVE MIRROR
OBJECT
LOCATION
Between F
and mirror
Between C
and F
Beyond C
IMAGE CHARACTERISTICS
SIZE
ATTITUDE
(smaller, larger, or same)
(inverted or upright)
LOCATION
TYPE
(Real or virtual)
SUMMARY: IMAGE CHARACTERISTICS
OF A CONCAVE MIRROR
OBJECT
LOCATION
IMAGE CHARACTERISTICS
SIZE
ATTITUDE
LOCATION
TYPE
(smaller, larger, or same)
(inverted or upright)
Between F
and mirror
LARGER
UPRIGHT
BEHIND
MIRROR
VIRTUAL
Between C
and F
LARGER
INVERTED
BEYOND C
REAL
Beyond C
SMALLER
INVERTED
BETWEEN
C&F
REAL
(Real or virtual)
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