concave mirrors can form real inverted images. topic4.4 (pages 314-317) today we will... have a...

Concave Mirrors Can Form Real Inverted Images.Concave Mirrors Can Form Real Inverted Images.

Topic Topic 4.44.4

(Pages 314-317)

TODAY WE WILL...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 CRITERIASUCCESS CRITERIA- You will be successful if you can draw the

images of the objects for all three concave mirror scenarios.

LAST WEEK WE COVERED ...

LAWS OF REFLECTION

IMAGES IN PLANE MIRRORS

THIS WEEK WE COVERED ...

CONCAVE MIRRORS

LET’S REVIEW ...

Copyright © 2010 McGraw-Hill Ryerson Ltd.

The angle of reflection is equal to the angle of incidence.The angle of reflection is equal to the angle of incidence.

Copyright © 2010 McGraw-Hill Ryerson Ltd.

The Law of ReflectionThe Law of Reflection

The Law of Reflection applies to every reflecting surface. The word “plane” refers to any flat surface.

WHAT IS AN IMAGE?WHAT IS AN IMAGE?

IMAGE: a picture or reproduction of an object formed using light.

When you see an object reflected in a mirror, you do not see the object itself.

Instead, you see an IMAGE of the object.

Copyright © 2010 McGraw-Hill Ryerson Ltd.

Ray Diagrams for Plane MirrorsRay 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.

CHARACTERISTICS OF IMAGESIN A PLANE MIRROR CHARACTERISTICS OF IMAGESIN A PLANE MIRROR

Describe the image characteristics for an image in a plane (flat) mirror.

SIZE:

ATTITUDE:

LOCATION:

TYPE:

Same size as the object.

Upright ... Image is oriented in the same direction as the object.

Image is behind the mirror, and the image distance is equal to the object distance.

The image is virtual.

Curved MirrorsThere are two types of

curved mirrors:

Concave (converging) Convex (diverging)

Concave Mirrors

PrincipleAxis (PA) Focus (F)

Centre of Curvature (C)

Vertex (V)

Focal length (f)

2 times the focal length (2f)

Concave mirrors ... termsConcave 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 themirror fits on. The focal point is exactlyhalfway 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 4.4CWORKSHEET 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 MirrorsRECALL ... Ray Diagrams for Concave Mirrors

Locating Images in Concave Mirrors

RULES:1. The first ray is drawn

parallel to the principal axis, and it will reflect back through the focal point.

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.

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.

Copyright © 2010 McGraw-Hill Ryerson Ltd.

Ray Diagrams for Objects betweenF and C for Concave MirrorsRay Diagrams for Objects betweenF and C for Concave Mirrors

Pg.314

Copyright © 2010 McGraw-Hill Ryerson Ltd.

Ray Diagrams for Objects betweenF and C for Concave MirrorsRay Diagrams for Objects betweenF and C for Concave Mirrors

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

Pg.314

Copyright © 2010 McGraw-Hill Ryerson Ltd.

Ray Diagrams for Concave MirrorsRay Diagrams for Concave Mirrors

Copyright © 2010 McGraw-Hill Ryerson Ltd.

Concave mirrors can form upright, virtual images.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 PointRay 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 PointRay 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 PointRay Diagrams for an Object between a Concave Mirror and the Focal Point

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

Pg.317

Ray Diagrams for Concave MirrorsRay Diagrams for Concave Mirrors

Ray Diagrams for anObject beyond CRay Diagrams for anObject 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.

• 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

Ray Diagram for an object located beyond C

The 4 characteristics of the image of an object placed beyond C are:

OBJECT IMAGE CHARACTERISTICS

LOCATION

SIZE(smaller, larger, or

same)

ATTITUDE

(inverted or upright)

LOCATION

TYPE(Real or virtual)

Between F and mirror

Between C and F

Beyond C

SUMMARY: IMAGE CHARACTERISTICS OF A CONCAVE MIRROR

OBJECT IMAGE CHARACTERISTICS

LOCATION

SIZE(smaller, larger, or

same)

ATTITUDE

(inverted or upright)

LOCATION

TYPE(Real or virtual)

Between F and mirror

LARGER UPRIGHT BEHIND MIRROR VIRTUAL

Between C and F

LARGER INVERTED BEYOND C REAL

Beyond C SMALLER INVERTED BETWEENC & F REAL

SUMMARY: IMAGE CHARACTERISTICS OF A CONCAVE MIRROR