1. Optics Lesson 3 Introduction to Reflection and Plane Mirrors

2. Terminology of Reflection
Perpendicular
Parallel

3. Terminology of Reflection

4. Terminology of Reflection
Plane Mirror (Flat Mirror)
Concave Mirror (caved inwards)
Convex Mirror (bumped out towards you)

5. Reflection
The law of reflection – The angle of incidence is equal to the angle of reflection Each arrow represents a “ray” of light.
Angle of Incidence
Angle of Reflection
Note: The angles are not measured to the edge They are measured to the “normal”
The normal is a doted line that is drawn perpendicular to the mirror.

6. Reflection from a mirror
Normal
Incident ray
Reflected ray
Angle of incidence
Angle of reflection
Mirror

7. Angle of incidence = Angle of reflection
The Law of Reflection
Angle of incidence = Angle of reflection
In other words, light gets reflected from a surface at the same angle it hits it.
The same !!!

8. Types of Reflection Clear Reflection: Diffuse Reflection:
Reflection of light off a smooth surface
Diffuse Reflection:
Reflection of light off an irregular survafe

9. Clear vs. Diffuse Reflection
Smooth, shiny surfaces have a clear reflection:
Rough, dull surfaces have a diffuse reflection.
Diffuse reflection is when light is scattered in different directions

10. Clear Reflection
Diffuse Reflection

11. Ray Diagrams
A ray diagram is a method used to determine where an image will appear when an object is viewed through a mirror or lens A light ray radiates rays in millions of directions but we are only concerned with the ones that reach our eyes

12. Locating an Image in a Mirror
Since we know light travels in a straight line our brains think that the source is actually behind the mirror
This is called a virtual because the image location we perceive is not real
Note, dashed lines indicate light rays behind the mirror

13. We can use light rays and the laws of reflection to determine where our object is located and draw it. We do this using object-image lines
Rules for object-image lines
The distance between the object and mirror = the distance between the mirror and image
The object-image line is perpendicular to the mirror surface

14. By choosing enough points we can accurately locate and draw our virtual image

15. The Result - Lateral Inversion
The orientation of an image in a plane mirror is flipped horizontally and in reverse order
Try it for your self L

16. Lateral Inversion Ambulance SCIENCE!
- Why do you think they paint it backwards?

17. SALT
When you describe the properties of an image, you need to examine four characteristics
Size of image (compared to the object: same size, smaller, larger)
Attitude of image (which way the image is orientated compared to the object: upright or inverted)
Location of image (distance from mirror)
T ype of image (real or virtual)

18. SALT
An image in a plane mirror is ALWAYS the same size as the object, upright, equal distance behind the mirror virtual (behind the mirror)