1. Optics Lesson 4 Reflection In Curved Mirrors

2. Terminology
Centre of curvature (C) – Middle of the “circle” Focus (focal point) (F) – Where reflected rays all intersect Principal Axis (PA) – The line drawn through the centre of the mirror (and meeting the mirror at 90°) Vertex (V) – The exact point where the PA meets the mirror.

3. Recall
Light rays always have an Angle of Reflection = Angle of Incidence
This equal angle is between the ray and the normal with is a90° to the mirrors surface at the point where the ray hits the mirror
Angle of Incidence
Angle of Reflection
Normal (90° to mirror surface)

4. Terminology
Concave Mirrors – are also known as converging mirrors as the light converges at the focus in front of the mirror and creates a real image.
Mirror is “caved” in
Convex Mirrors – are also known as diverging mirrors as the focus is found behind the mirror (virtual image) and is found by tracing back the reflected rays in a straight line.

5. Focal Point – Concave Mirror
We can use parallel rays to PA to find the focal length of a concave mirror. All parallel lines will reflect into the focal point *note the normal is 90° to the point on the mirror where the ray strikes The focal point for a concave mirror is to the left

6. Concave Mirror Rules

7. Concave Mirror Rules

8. Concave Mirror Rules

9. Concave Mirror Rules

10. Ray Diagrams – Concave Mirrors
You need 2 rays to locate an image.
The image is located where the rays intersect.
If the rays do not intersect, you need to trace them back to the point where they intersect.
You need to include 2 basic rays.
A parallel ray is reflected to the mirror then through the “focal point”
A ray is sent through the focal point is reflected parallel to the principal axis. F

11. Ray Diagrams Describing Images Small than object
S – Size (Larger, Smaller, Same)
Inverted
A – Attitude (Upright or inverted)
Between C and F
L – Location (How far from the mirror?)
Real
T – Type (Real or Virtual) F

12. Object beyond C

13. Object at C

14. Object between C and F

15. Object at F

16. Object between F and mirror

17. Properties of a Converging Mirror p. 499

18. Uses of Concave Mirrors
Searchlights, car headlights and flashlights all use concave mirrors to create parallel or almost parallel beams of light (Why?)
Telescopes and satellite dishes use concaves mirrors to focus electromagnetic waves at the focal point (Why?)

19. Uses of Concave Mirrors Con’t
We can also use concave mirrors to magnify a reflection close up. Why does it give this type of reflection?

20. End of Day 1

21. Optics Lesson 4 Reflection In Curved Mirrors

22. Recall
Light rays always have an Angle of Reflection = Angle of Incidence
This equal angle is between the ray and the normal with is a90° to the mirrors surface at the point where the ray hits the mirror
Angle of Incidence
Angle of Reflection
Normal (90° to mirror surface)

23. Terminology
Concave Mirrors – are also known as converging mirrors as the light converges at the focus in front of the mirror and creates a real image.
Mirror is “caved” in
Convex Mirrors – are also known as diverging mirrors as the focus is found behind the mirror (virtual image) and is found by tracing back the reflected rays in a straight line.

24. Focal Point – Convex Mirror
The focal point for a convex mirror is to the right.
It can be found by drawing lines parallel to the PA towards the mirror
Extend the reflected lines past the mirror
Where the imaginary lines intercept is the focal point

25. Centre of sphere – Convex Mirror
The C for a convex mirror is to the right.
It can be found by drawing a line perpendicular to the mirror at any point
Extend the reflected lines past the mirror
Where the imaginary lines intercept the PA is the C

26. Convex Mirror Rules
The difference between a concave mirror and a convex mirror is that in a convex mirror, F (now called a virtual focus) and C are behind the mirror and light rays seem to come from an apparent light source behind the mirror

27. Convex Mirror Rules

28. Convex Mirror Rules

29. Convex Mirror Rules

30. Ray Diagrams – Convex Mirrors
The image is located where the extended reflected lines intersect behind the mirror
You need to include 2 basic rays.
A parallel ray that extends from the top of the object to the mirror and is reflected back to the viewer
A ray is directed towards the focal point and is reflected parallel to the principal axis.
Extend the reflected rays past the mirror until they intersect
The point of intersection is the top of the image. The image extends down to the Principal axis

31. Images in a Convex Mirror
The rays reflected off a convex mirror always diverge
Reflected rays from an object never cross in front of the mirror to form a real image
Instead it ALWAYS creates a smaller, upright, virtual image

32. Uses of Convex Mirrors
Convex mirrors show a wide range of view with their smaller virtual image .
Used in:
Security mirrors
Side-view mirrors in cars
“Objects in mirror are closer than they appear” ??????

33. One More Demonstration Concave vs. Convex Curved Mirrors http://www