10.3 Images in Concave Mirrors Copyright © 2010 McGraw-Hill Ryerson Ltd. How does a concave mirror change the size, shape, and orientation of objects reflected in it? (Page 419)

What is a concave mirror? A.K.A. “Converging mirror”  Causes light rays to meet at a single point in front of the mirror  Laser Demo!

Properties of Concave Mirrors Copyright © 2010 McGraw-Hill Ryerson Ltd. A concave mirror has reflecting surfaces that curve inward (like a cave) Vocabulary terms that will help you understand how concave mirrors work: The principal axis is the line that passes through the centre of curvature (C) of the mirror and is normal to the centre of the mirror. The focal point (F) is the point on the central axis through which reflected rays pass when the incident rays are parallel to and near the principal axis. The focal length (f) is the distance between the vertex (V) of a mirror and the focal point. The vertex (V) is the middle point of a curved mirror The centre of curvature (C) is located at 2X the focal length (f) on the principal axis. **Note: All incident rays that pass through the centre of curvature will reflect back on themselves (Page 420)

If it helps, think of this: Concave mirror = many small flat mirrors side by side Focal point

Concave Mirror Ray Diagrams It is vitally important that you use a ruler or the straight side of your protractor to draw STRAIGHT lines Textbook reference: – Page

Concave Mirror Ray Diagrams Ray 1 - travels parallel to the principal axis and reflects through the focal point (F) “in parallel out through the focus”

Concave Mirror Ray Diagrams Ray 2 - travels through the focal point and reflects parallel to the principal axis “in through the focus, out parallel”

Concave Mirror Ray Diagrams The point where the two reflected rays converge will be the location of the image

Concave Mirror Ray Diagrams A third ray (shown in red) should be drawn as a “check” This can only be used if the Centre of Curvature (“C”) is present in the diagram – which is usually 2X focal length. “in through C out through C”

You try! There are 5 “cases” we will be investigating  The cases refer to the object location, not the image location, in relation to the various points of reference along the principle axis (i.e. focal point, centre of curvature, vertex, etc.)

Concave Mirror Reflections 5 Cases for location of OBJECT (not image!) 1.Object is greater than 2 focal lengths from the mirror (d o >2f) – note: 2f = C 2.Object is at 2 focal lengths/Centre of Curvature (2f/C) 3.Object is between 1 and 2 focal lengths from the mirror (f<d o <2f) 4.Object is at the focal point (d o =f) 5.Object is between the mirror and the focal point (V<d o <f)

Case 1: Object beyond 2f/C LocationOrientationSizeType F<di<2FInvertedReducedReal C

Case 2: Object at 2f/C LocationOrientationSizeType At CInvertedSameReal

Case 3: Object between 2f and F LocationOrientationSizeType di>CInvertedEnlargedReal C

Case 4: Object at F LocationOrientationSizeType No Image Formed!

Case 5: Object between F and V LocationOrientationSizeType Opposite side of mirror UprightEnlargedVirtual

HOMEWORK Page 425 # Page 430 # 1, 2, 4, 8

Ray Diagrams for Concave Mirrors (object between F and the mirror) Copyright © 2010 McGraw-Hill Ryerson Ltd. (Page 422)

Ray Diagrams for Concave Mirrors (object between F and the mirror) Copyright © 2010 McGraw-Hill Ryerson Ltd. (Page 422)

Ray Diagrams for Concave Mirrors (object between F and C] Copyright © 2010 McGraw-Hill Ryerson Ltd. A real image is an image that is formed when reflected rays meet. (Page 423)

Ray Diagrams for Concave Mirrors (object between F and C) Copyright © 2010 McGraw-Hill Ryerson Ltd. (Page 423)

Ray Diagrams for Concave Mirrors (object beyond C] Copyright © 2010 McGraw-Hill Ryerson Ltd. (Page 424)

Ray Diagrams for Concave Mirrors (object beyond C) Copyright © 2010 McGraw-Hill Ryerson Ltd. (Page 424)