1. Aim: How do we explain the law of reflection?

2. The Law of Reflection

3. Normal Line
The normal line is a line drawn perpendicular to the surface. The angle of incidence is the angle at which light strikes a surface with respect to the normal. The angle of reflection is the angle at which light reflects from a surface with respect to the normal.

4. Law of Reflection
Light travels in straight line paths. When light reflects, the angle of incidence must be equal to the angle of reflection.

5. Problem 1
Consider the diagram at the right. Which one of the angles (A, B, C, or D) is the angle of incidence? ___B___ Which one of the angles is the angle of reflection? ___C___

6. Problem 2
2. A ray of light is incident towards a plane mirror at an angle of 30-degrees with the mirror surface. What will be the angle of reflection? 60 degrees

7. Problem 3
3. A ray of light is approaching a set of three mirrors as shown in the diagram. The light ray is approaching the first mirror at an angle of 45-degrees with the mirror surface. Trace the path of the light ray as it bounces off the mirror. Continue tracing the ray until it finally exits from the mirror system. How many times will the ray reflect before it finally exits? 2 times

8. Find the angle between the light ray and the normal when the light ray bounces off of the titled mirror. 40 degrees

9. Specular vs. Diffuse Reflection
Specular reflection-reflection off a smooth surface. (You can see yourself) Diffuse reflection- reflection off a rough surface

10. Specular or Diffuse?
Specular

11. Applications of Diffuse Reflection

12. Questions
If a bundle of parallel incident rays undergoing diffuse reflection follow the law of reflection, then why do they scatter in many different directions after reflecting off a surface? The normal is in different directions along a rough surface.
Perhaps you have observed magazines which have glossy pages. The usual microscopically rough surface of paper has been filled in with a glossy substance to give the pages of the magazine a smooth surface. Do you suppose that it would be easier to read from rough pages or glossy pages? Explain your answer.
Rough pages. Glossy pages reflect too much light, leaving a glare.

13. Why? The light reflects off both the inner and outer surface

14. Image Formation

15. Image Formation
The image is located at the point where the reflected rays appear to be converging from.

16. Draw images Draw the reflection of a point
Draw the reflection of a line

17. Plane Mirrors Reflection from plane mirrors Preserve distance
Preserve size
Reverse left-right polarity

18. What is the required length of a mirror so that you can see your entire body?