1. Images in Curved Mirrors

2. Learning Goals
To learn more about the differences between concave and convex mirrors
To learn how to predict and locate images in concave and convex mirrors

3. Introduction
Curved mirrors are created when you make part of the surface of a sphere reflective
If the reflection is from the inner surface of the sphere, the mirror is concave.
The centre of a concave mirror bulges away from you

4. Introduction
In a convex mirror, the reflection is from the outer surface of the sphere
The centre of a convex mirror bulges

7. Terminology
The centre of curvature of a mirror is the centre of the sphere, part of whose surface forms the curved mirror
It is labelled as C

8. Terminology
The principal axis of the mirror is the line going through the centre of curvature and the centre of the mirror

9. Terminology
Because the principal axis goes through the centre of the circle, this axis is a radius of the circle
This means that the principal axis intersects the mirror at 90° and is normal to the surface
The vertex is the point where the principal axis intersects the mirror
It is labelled as V

10. Terminology
Any light rays that are parallel to the principal axis will be reflected off the mirror through a single point
This point is where all the parallel light rays come together, or “converge” is called the focus
It is labelled as “F”
Because a concave mirror focuses parallel rays at F, this type of mirror is also called a converging mirror

11. Terminology

12. How to Locate the Image in a Converging (Concave) Mirror

13. Images in a Concave Mirror
To determine the image of an object in front of a concave mirror, you need to draw at least two incident rays from the top of the object
These rays will be reflected off the mirror and may or may not cross to form an image.

14. Images in a Concave Mirror
Images in a Concave Mirror

16. Images in a Converging Mirror
If you place a luminous source at a distance greater than C, you can locate an image of this source by moving a paper screen back and forth in front of the mirror

17. Images in a Converging Mirror
The image is smaller, inverted, and somewhere between C and F
In this case, light is actually arriving at the image location
This type of image is called a real image
Any image that can be formed on a screen is a real image because light rays are actually arriving at the image location

18. Images in a Converging Mirror
When an object is:
Beyond C (example a)
At C (example b)
Between C and F (example c)
The reflected rays actually meet in front of the mirror, forming an inverted, real image each time
Many devices make use of the properties of concave mirrors

20. Images in a Converging Mirror
In a searchlight, the light source (the filament) is at the focus, and the reflected rays form a parallel beam

21. Images in a Converging Mirror
No real image is produced when an object is located at F in front of a concave mirror
The reflected rays are parallel and do not intersect to form an image
If you extend the rays behind the mirror using dashed lines, you cannot even see a virtual image

22. Images in a Converging Mirror
No real image is produced when an object is between F and the concave mirror
The reflected rays spread apart, or diverge

23. Images in a Converging Mirror
The human brain, interprets these diverging rays backwards to where they appear to originate, which in this case is behind the mirror
This results in a virtual image because the concave mirror is opaque
These extrapolated rays cannot actually come from behind the mirror

24. Images in a Converging Mirror
A virtual image behind a concave mirror is always larger and upright
A shaving mirror and a makeup mirror are two common examples that make use of this property

25. Summary

26. How to Locate the Image in a Diverging (Convex) Mirror

27. Images in a Convex Mirror
The parts of a convex mirror and the imaging rules for a convex mirror are similar to those for a concave mirror

28. Images in a Convex Mirror
The difference is that:
F is now called a virtual focus
C and F are behind the mirror
Light rays seem to come from an apparent light source behind the mirror

29. Images in a Convex Mirror

30. Images in a Convex Mirror
The rays reflected off a convex mirror always diverge
Diverge means to spread out
For this reason, a convex mirror is also called a Diverging Mirror
Reflected rays from an object never cross in front of the mirror to form a real image
The human brain interprets these rays as being behind the mirror to where they appear to converge.

31. Images in a Convex Mirror
Images in a Convex Mirror
This results in the diverging (convex) mirror producing a smaller, upright, virtual image.
This property makes convex mirrors very useful as security mirrors in stores

32. Images in a Convex Mirror

33. Images in a Convex Mirror
Convex mirrors show a wide range of view with their smaller virtual image
Convex mirrors are also used as the side-view mirror on vehicles
“Objects in mirror are closer than they appear” is frequently printed at the bottom of side-view mirrors to remind viewers that they are seeing a smaller image