2. Reflection & Mirrors
Topic 13.3 (3 part lesson)

3. Outcomes
You will describe, quantitatively, the phenomena of reflection and refraction, including total internal reflection

4. Light as a Wave
Like mechanical waves, light, obeys the law of reflection
LAW OF REFLECTION: The angle of incidence is equal to the angle of reflection (this is TRUE for all surfaces)

5. Virtual vs. Real Images
virtual image: an image from which light rays appear to come; cannot be formed on a non-reflective surface or screen (upright)
Example: mirrors can produce virtual images
real image: an image from which light rays come; can be formed on a diffusely reflecting surface or screen (upside down)
Example: a projector projecting an image on a screen

6. Mirrors: Ray Diagrams/Calculations

7. Day #2 - Outcomes
You will use ray diagrams to describe an image formed by thin lenses and curved mirrors.
You will describe, quantitatively, simple optical systems, consisting of only one component, for both lenses and curved mirrors.

8. Types of Mirrors There are two types of spherical mirrors:
1. CONCAVE CONVEX
2. CO

9. Curved Mirror Terms
Center of curvature - The location of the center of the imaginary sphere is called the center of curvature, C, of the mirror
Radius of curvature - The distance from the center of curvature to the mirror
Vertex (V) – The geometric centre of the curved mirror surface
Principal axis - A line drawn through the center (vertex) of the mirror
Principle focal point - The point light rays reflect to if they hit the mirror parallel to the principal axis on a concave mirror (or the point the light rays appear to diverge from in a convex mirror).
Focal length - Distance from the center of the mirror to the focal point. This distance is always half the radius of curvature.

10. Concave mirrors are also called converging mirrors
Concave mirrors are also called converging mirrors. They have a real focal point. These mirrors can produce real images, no image, or virtual images.
Convex mirrors are also called diverging mirrors. They have a virtual focal point. These mirrors only produce virtual images.

11. Drawing Ray Diagrams
Ray diagrams are used to find the characteristics of an image produced by a curved mirror.
Steps for drawing ray diagrams:
1. Draw the mirror showing the principal axis, the center of curvature, and the principle focal point

12. Drawing Ray Diagrams
2. Place a vertical arrow on the principal axis to illustrate the position and size of the object.

13. Drawing Ray Diagrams
3. Draw two rays from the top of the object to the mirror
First ray parallel to the principal axis and reflected through focal point
Second ray through the centre of curvature
*Where the rays intersect is where the new image is.
We’ll practice drawing ray diagrams in our sample problems.

14. Mirror Equations and Magnification
Magnification is calculated with the following equations:
Where, hi = height of image and ho = height of object

15. Determining other Characteristics

16. Sign Conventions
Real images/distances, concave focal lengths & erect images= positive (+)
Virtual images/distances, convex focal lengths & inverted images = negative (-)
Note:
*all real images are inverted and all virtual images are erect
*do and ho are always +

17. Sample Problem
An object is positioned 10 cm from a mirror of focal length 25 cm forming a larger, virtual image. Calculate di, and the magnification of the mirror. Draw a ray diagram as part of your answer.

18. Sample Problem
A 15.0 cm tall object is placed 40.0 cm from a mirror of radius of curvature 20.0 cm. The mirror produces a smaller, virtual image. Calculate di, magnification, and hi. Draw a ray diagram as part of your answer.

19. Homework Go through HANDOUT as class Mirror Drawing Handout
Concept Q’s: p.665 #1, 4, 5 & 7
Calculation Q’s: p. 102 #1-8 & p.106 #2 – 12 (workbook)