Textbook Reference 10.3 (P.419-430) Concave (converging) Mirrors
Learning Goals • Understand how to draw ray diagrams for concave mirrors • Be able to identify when images are real or virtual Success Criteria • To draw at least one ray diagram for concave mirrors and to identify if the image is real or virtual.
Curved Mirrors Mirrors 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).
Types of Curved Mirrors • 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.
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.
Concave Mirrors Light comes from this side Vertex Centre of Curvature (C) Principle Axis (PA) Focal length Focus (F)
Locating Images in Concave Mirrors • To determine the image of an object in from 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.
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) meet • Located in the front of the mirror • You need a screen to see the real image
EXAMPLE ... FIND THE IMAGE SALT ... SIZE (smaller, larger, or same), ATTITUDE (upright or inverted), LOCATION, and TYPE (real or virtual) SALT ... SIZE = Larger ATTITUDE = Inverted LOCATION = Beyond C TYPE = Real
JIGSAW There 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 GROUPS GROUP 1 GROUP 2 GROUP 3 GROUP 4 GROUP 5 Adoma Julia Akin Haya Angelica Annamaria Anthony Victor Andre Alex Helder Stephanie Michael IvoCristian Vanessa Jonathan Alissia Josie Gabriel David Abdullah Higor Matthew Sevak Stephen Raffaela Rachel Victoria
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.