- Concave mirrors are shaped like the inner part of a sphere and convex mirrors are shaped like the outer part. - A concave mirror acts as a converging mirror that forms a real focal point in front of the mirror, while a convex mirror acts as a diverging mirror that forms a virtual focal point behind the mirror. - For concave mirrors, rays parallel to the principal axis pass through the focal point and rays through the center of curvature are reflected back along themselves. For convex mirrors, rays parallel to the principal axis appear to diverge from the focal point and rays through the center are reflected back on themselves.

1. CURVED MIRRORS

2. • Concave mirrors are shaped
like part of the inside of a
sphere
• Convex mirrors are shaped like
part of the outside of a sphere
CURVED MIRRORS

3. Centre of
sphere
Concave mirror Convex mirror
CURVED MIRRORS

4. Centre of Curvature ‘C’ = centre of the sphere of which the curved mirror forms a part.
Pole ‘P’ = midpoint of the mirror (a.k.a. vertex)
Principal Axis = straight line passing through the pole and the centre of curvature of a
spherical mirror.
Normal = straight line joining any point of a curved mirror with the centre of curvature
C of the mirror.
CURVED MIRROR TERMS

5. CONCAVE MIRRORS

6. • Rays of light parallel to the principal axis of a mirror, reflect through a point (in
case of a concave mirror) on the principal axis. This point is the focus or focal
point ‘f’ of the mirror.
• A concave mirror is also known as a converging mirror
• The focus is in front of the mirror.
• The focus is real as the rays of light after reflection converge at the focus.
CONCAVE MIRRORS

7. 1) A light ray parallel to the principal axis is reflected
through F
2) A light ray through C is reflected back onto itself
3) A light ray through F will reflect parallel to the
principle axis
4) A light ray aimed at the vertex will follow the Law of
Reflection (angle of incidence = angle of reflection)
CONCAVE MIRROR RAYS

8. 1) A light ray parallel to the principal axis is reflected through F
C F
CONCAVE MIRROR RAY 1

9. 2) A light ray through C is reflected back onto itself
C F
CONCAVE MIRROR RAY 2

10. 3) A light ray through F will reflect parallel to the principle axis
C F
CONCAVE MIRROR RAY 3

11. 4) A light ray aimed at the vertex will follow the Law of
Reflection (angle of incidence = angle of reflection)
C F V
CONCAVE MIRROR RAY 4

12. Only two light rays are needed to locate an
image
1) A light ray parallel to the principal axis is reflected through F
2) A light ray through C is reflected back onto itself
3) A light ray through F will reflect parallel to the principle axis
4) A light ray aimed at the vertex will follow the Law of
Reflection (angle of incidence = angle of reflection)
LOCATING AN IMAGE ON A CONCAVE MIRROR

13. LOCATING AN IMAGE ON A CONCAVE MIRROR

14. LOCATING AN IMAGE ON A CONCAVE MIRROR

15. LOCATING AN IMAGE ON A CONCAVE MIRROR

16. Object is between F and C of a
concave mirror:
•the image is larger than the
object
•the image is inverted
•the image is farther from the
mirror than the object is
•the image is real
DESCRIBING IMAGE ON A CONCAVE MIRROR

17. LOCATING AN IMAGE ON A CONCAVE MIRROR

18. LOCATING AN IMAGE ON A CONCAVE MIRROR

19. LOCATING AN IMAGE ON A CONCAVE MIRROR

20. LOCATING AN IMAGE ON A CONCAVE MIRROR

21. Object is between F and the
concave mirror:
•the image is larger than
the object
•the image is upright
•the image is behind the
mirror
•the image is virtual
DESCRIBING IMAGE ON A CONCAVE MIRROR

22. LOCATING AN IMAGE ON A CONCAVE MIRROR

23. CONVEX MIRRORS

24. • In a convex mirror, rays of light (parallel to the principal axis of a mirror), appear to
diverge from a point on the principal axis. This point is the focus or focal point ‘f’
of the mirror.
• A convex mirror is also known as a diverging mirror
• The focus is behind the mirror
• The focus is virtual as the rays of light after reflection appear to come from the
focus behind the mirror
CONVEX MIRRORS

25. 1) A ray parallel to the principal axis is reflected as if it
had come through F
2) A ray aimed at C is reflected back upon itself
3) A ray aimed at F is reflected parallel to the principal
axis
CONVEX MIRROR RAYS

26. 1) A ray parallel to the principal axis is reflected as if it had come through F
F C
Any lines past a mirror are NOT
light rays. They are represented
as dotted lines.
CONVEX MIRROR RAY 1

27. 2) A ray aimed at C is reflected back upon itself
F C
CONVEX MIRROR RAY 2

28. 3) A ray aimed at F is reflected parallel to the principal axis
F C
CONVEX MIRROR RAY 3

29. Only two light rays are needed to locate an image
1) A ray parallel to the principal axis is reflected as if it had come
through F
2) A ray aimed at F is reflected parallel to the principal axis
LOCATING AN IMAGE ON A CONVEX MIRROR

30. LOCATING AN IMAGE ON A CONVEX MIRROR

31. LOCATING AN IMAGE ON A CONVEX MIRROR

32. LOCATING AN IMAGE ON A CONVEX MIRROR

33. LOCATING AN IMAGE ON A CONVEX MIRROR

34. The image of an object in a
convex mirror will have the
following characteristics:
•the image is smaller than
the object
•the image is upright
•the image is closer to the
mirror than the object is
•the image is virtual
The images in convex mirrors are
much more similar to each other
than those in concave mirrors.
DESCRIBING AN IMAGE ON A CONVEX MIRROR
Homework: Page 501 #6-10

35. CALCULATIONS WITH MIRRORS

36. Variables
F = Focal Point C = Centre of Curvature V = Vertex
do = Object Distance di = Image Distance f = Focal Length
ho = Object Height hi = Image Height
CALCULATIONS WITH MIRRORS

37. CALCULATIONS WITH MIRRORS
1. In the diagram below, the object is between the mirror and F. Use the data in the
diagram to answer the questions below.
a) Calculate the image distance.
b) Calculate the image height.
a) Given:
ho = 1 cm
do = 1 cm
f = 2 cm
1 = 1 + 1
f di do
1 = 1 + 1
(2) di (1)
1 – 1 = 1
2 1 di
1 – 2 = 1
2 2 di
– 1 = 1
2 di
– 2 = di
.: the image distance
is 2 cm behind the
mirror

38. CALCULATIONS WITH MIRRORS
1. In the diagram below, the object is between the mirror and F. Use the data in the
diagram to answer the questions below.
a) Calculate the image distance.
b) Calculate the image height.
b) Given:
ho = 1 cm
do = 1 cm
f = 2 cm
di = - 2 cm
m = hi = - di
ho do
hi = - di
ho do
hi = - (-2)
(1) (1)
hi = 2
.: the image height is 2 cm
upright