1. Mirror Equations
Lesson 4

2. Objective
Quantitatively determine the relationship between the focal length and distance an object and its image are from the mirror.

3. Mirror or Lens Equations
Equations that are used to indicate the location of an image or to find the image distance, di.

4. Eg) Concave mirror
object
image
Mirror Equation:

5. Magnification equation:
compares the size of the object to the size of the image

6. Rules For Mirrors The object distance, do, is always positive
If the image distance, di, is positive, then the image is real
If the image distance, di, is negative, then the image is virtual

7. Rules for Mirrors
Upright objects or images have positive values for ho and hi
Inverted objects or images have negative values for ho and hi
Converging (Concave) mirrors have positive focal lengths while Diverging mirrors have negative focal lengths

8. Example #1) An object 2. 50 cm high is 20
Example #1) An object 2.50 cm high is 20.0 cm from a concave mirror having a radius of curvature of 15.0 cm
a. Sketch a ray diagram to show where the image is located
object
image

9. b. Determine the location of the image
c. Determine

10. Convex Mirror
A convex mirror reflects light from its outer surface and produces a virtual image
Aka: Diverging mirror

11. Example #2
An object is placed 30 cm from a diverging mirror, whose focal length is 10 cm.
Determine:
the image distance.
if the image is real or virtual.
if the image is erect or inverted.
the image magnification.

12. Diagram

13. Calculation

14. Calculation of magnification

15. Determination of image attitude

16. Eg) An object is placed 10.0 cm from a convex mirror that has a focal length of -15.0 cm.
a. Sketch a ray diagram to show the location of the image.
object
-15.0 cm

17. c. Determine the magnification of the image
b. Determine
c. Determine the magnification of the image

18. Summary: Sign Convention: Distance (d) Height (h)
real focal points or images upright images +
virtual focal points or images inverted images -

19. Equations for a Curved Mirror