Concave (converging) Mirrors

Textbook Reference 10.3 (P.419-430)

Learning GoalsUnderstand how to draw ray diagrams for

concave mirrorsBe able to identify when images are real

or virtual

Success CriteriaTo draw at least one ray diagram for

concave mirrors and to identify if the image is real or virtual.

Curved MirrorsMirrors with a single curvature

find many uses in our homes and optical devices. To make a curved mirror, you must make part of the surface of the sphere reflective. There are two types of curved mirrors:

Concave (converging) Convex (diverging).

1. Concave (Converging) Mirror:• Shaped like part of the surface of a sphere in

which the inner surface is reflective.• For example, similar to the surface of a bowl.

2. Convex (Diverging) Mirror:• Shaped like part of the surface of a sphere in

which the outer surface is reflective.

Types of Curved Mirrors

Concave Mirror Terminology

Centre of Curvature:The centre of the sphere whose surface has been used to make the mirror.

Its the point at which the normals meet. Labelled C.Principal Axis:

The line through the centre of curvature to the midpoint of the mirror.Vertex:

The point where the principal axis meets the mirror. Labelled V.Focus or Focal Point:

The point at which light rays parallel to the principal axis converge (meet at a common point) when they are reflected off a concave mirror. Labelled F.

Principle Axis (PA)

Focus (F)

Centre of Curvature (C)

Vertex

Concave Mirrors

Focal length

Light comesfrom this side

Locating Images in Concave MirrorsTo determine 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. A light ray parallel to the

principal axis is reflected through the focus.

Locating Images in Concave Mirrors

RULES ... Cont`d:2. A light ray through the centre

of curvature is reflected back into itself.

3. A ray through the focus will reflect parallel to the principal axis.

4. A ray aimed at the vertex will follow through the law of reflection.

EXAMPLE ... FIND THE IMAGE

Recall what a REAL IMAGE is ...A Real Image is an image that can be seen on a

paper screen as a result of light rays actually arriving at the image location.

Real Image:Formed when reflected rays (not extended rays)

meetLocated in the front of the mirrorYou need a screen to see the real image

EXAMPLE ... FIND THE IMAGESALT... SIZE (smaller, larger, or same), ATTITUDE (upright or inverted), LOCATION, and TYPE (real or virtual)

SALT ...SIZE = LargerATTITUDE = InvertedLOCATION = Beyond CTYPE = Real

JIGSAWThere are 5 scenarios to investigate with Concave mirrors.You will be placed in groups and assigned a scenario to

work on, during which time you will become the `expert` on that scenario.

Afterwards, everyone will JIGSAW into another group where you will all have a turn to `teach` your new group members about your concave mirror scenario.

Please reference your textbook (p.422-424) during this activity.

JIGSAW GROUPSGROUP 1 GROUP 2 GROUP 3 GROUP 4 GROUP 5Adoma Julia Akin Haya

AngelicaAnnamaria Anthony Victor Andre AlexHelder Stephanie Michael Ivo

CristianVanessa Jonathan Alissia Josie GabrielDavid Abdullah Higor Matthew SevakStephen Raffaela Rachel Victoria

OBJECT IMAGE CHARACTERISTICSLOCATION

SIZE(smaller, larger, or

same)

ATTITUDE

(inverted or upright)

LOCATION

TYPE(Real or virtual)

Beyond C

At C

Between C and FAt F

Between F and mirror

SUMMARY: IMAGING PROPERTIESOF A CONVERGING MIRROR

OBJECT IMAGE CHARACTERISTICSLOCATION

SIZE(smaller, larger, or

same)

ATTITUDE

(inverted or upright)

LOCATION

TYPE(Real or virtual)

Beyond C SMALLER INVERTED BETWEEN C & F REAL

At C SAME INVERTED AT C REAL

Between C and F LARGER INVERTED BEYOND C REAL

At F NO CLEAR IMAGE

Between F and mirror

LARGER UPRIGHT BEHIND MIRROR VIRTUAL

SUMMARY: IMAGING PROPERTIESOF A CONVERGING MIRROR

The following 5 slides are for reference purposes.

Case 1: The object is located beyond C

- When an object is located beyond C, the image will always be located between C and the Focus.- The image will be inverted.- The image is reduced in size.- The image is real.

Case 2: The object is located at C

- When an object is located at C, the image will also be located C.- The image will be inverted.- The image is the same size.- The image is real.

Case 3: The object is located between C and F

- When an object is located between C and F, the image will be located beyond C.- The image is inverted.- The image is larger.- The image is real.

Case 4: The object is located at F

- When the object is located at F, there is no image formed. WHY- Light rays from the same point do not converge. Reflected rays are parallel and do not form images.

Case 5: The object is located in front of F (between F and the mirror)

- When an object is located between F and the mirror, the image will always be located somewhere on the opposite side of the mirror.- The image is upright.- The image is larger.- The image is virtual. This is because the rays diverge and our brain extrapolates the rays backwards to where they appear to originate.