Introduction to Reflection and Plane Mirrors

1. Introduction to Reflection and Plane Mirrors - Terminology of Reflection - Reflection from a mirror - The Law of Reflection - Types of Reflection - Ray Diagrams - Locating an Image in a Mirror - Lateral Inversion - Properties of an image

2. Terminology of Reflection Perpendicular Parallel

3. Recall - Terminology

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

5. Reflection 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. The law of reflection – The angle of incidence is equal to the angle of reflection Each arrow represents a “ray” of light.

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

7. Angle of incidence = Angle of reflection • The Law 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 (Specular) Reflection: • Reflection of light off a smooth surface • Diffuse Reflection: • Refection of light off an irregular surface

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 image 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 SCIENCE! Ambulance - 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) • Type of image (real or virtual)

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