1. Copyright © 2010 McGraw-Hill Ryerson Ltd. What is the law of reflection? How do mirrors form images? Topic4.4 (Pages 304-31)

2. Copyright © 2010 McGraw-Hill Ryerson Ltd. The angle of reflection is equal to the angle of incidence. The incident ray is the light ray travelling toward the mirror or other surface.

3. Copyright © 2010 McGraw-Hill Ryerson Ltd. The angle of reflection is equal to the angle of incidence. The reflected ray is the light ray that has “bounced” off a reflecting surface.

4. Copyright © 2010 McGraw-Hill Ryerson Ltd. The angle of reflection is equal to the angle of incidence. The normal is a line that is perpendicular to a surface such as a mirror.

5. Copyright © 2010 McGraw-Hill Ryerson Ltd. The angle of reflection is equal to the angle of incidence. The angle of incidence (i ) is the angle between the incident ray and the normal.

6. Copyright © 2010 McGraw-Hill Ryerson Ltd. The angle of reflection is equal to the angle of incidence. The angle of reflection (r) is the angle between the reflected ray and the normal.

7. 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.

8. Copyright © 2010 McGraw-Hill Ryerson Ltd. Reviewing the Law of Reflection Click the “Start” button to review the law of reflection.

9. Copyright © 2010 McGraw-Hill Ryerson Ltd. Plane mirrors form images that are nearly identical to the object. Any smooth, flat reflecting surface, such as a mirror, is called a plane mirror. Examples of plane mirrors are shown below. A and B, grooming mirrors C, dentist’s mirror D, security mirror E, camera viewfinder mirror What other examples of plane mirrors can you think of?

10. Copyright © 2010 McGraw-Hill Ryerson Ltd. Seeing Objects You “see” an entire object because reflected light from every part of the object is reaching your eyes. The lens of your eye focuses the rays, and your eyes send messages to your brain about the object.

11. Copyright © 2010 McGraw-Hill Ryerson Ltd. Images in Plane Mirrors When an object is put in front of a plane mirror, all of the light rays from the object strike the mirror and reflect from it according to the law of reflection. Your brain interprets the pattern of light that reaches your eye as an image of the object behind the mirror. The rays that reach your eye appear as if they are coming from a point behind the mirror.

12. Copyright © 2010 McGraw-Hill Ryerson Ltd. 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. The terms object, image, object distance, and image distance are used when drawing ray diagrams for plane mirrors.

13. Copyright © 2010 McGraw-Hill Ryerson Ltd. Ray Diagrams for Plane Mirrors 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.

14. Copyright © 2010 McGraw-Hill Ryerson Ltd. Drawing Ray Diagrams for Plane Mirrors To find the image of an object in a plane mirror, you need to find the image location of at least two points on the object. The next 3 slides outline the steps involved in drawing a ray diagram for plane mirrors.

15. Copyright © 2010 McGraw-Hill Ryerson Ltd. Drawing Ray Diagrams for Plane Mirrors

16. Copyright © 2010 McGraw-Hill Ryerson Ltd. Drawing Ray Diagrams for Plane Mirrors All images in plane mirrors have many of the same characteristics. A few are listed below: Size: image size is the same as the object’s size. Attitude: the image is always oriented in the same direction as the object. Location: the image distance is equal to the object distance. Type: virtual images located behind the mirror.