1. Properties of Light and Reflection
10.2
Properties of Light and Reflection

2. Reflection

3. Reflection
Reflection - the change in direction of a light ray when it bounces off a surface

4. Rays of Light
Light travels in a straight line (as long as it’s moving through the same medium)
Medium – the substance through which light travels
Ray-a straight line with an arrowhead that shows the direction in which light waves are travelling.
Ray diagrams - can be used to make predictions about appearance of objects

5. Ray Model of Light Represented by 1 arrow Represented by many arrows
Ray – A single unit of light
Represented by 1 arrow
Beam – A bundle of light rays travelling in one direction
Represented by many arrows

6. Definitions You Need to Know
incident ray – a ray of light that travels from a light source towards a surface
angle of incidence – angle between the incident ray and the normal in a ray diagram
normal - a line that is perpendicular to a surface where a ray of light meets the surface
reflected ray – a ray that begins at the point where the incident ray and the normal meet
angle of reflection – the angle between the reflected ray and the normal in a ray diagram
plane mirror – a mirror with a flat reflective surface

7. Laws of Reflection
The incident ray, the reflected ray, and the normal always lie on the same plane.
2. The angle of reflection is equal to the angle of incidence.
Law of reflection states that the angle of incidence equals the angle of reflection
r = i

8. Drawing Ray Diagrams
Normal – dotted line perpendicular to the surface (90◦ angle)

9. Ray Diagrams

10. Protractor
LET’S PRACTICE USING A PROTRACTOR

11. Images in Plane Mirrors
Plane Mirror – A mirror with a flat, reflective surface
Scientists call an object in front of a mirror the object, and they call what is seen in the mirror the image of the object.
Using the laws of reflection to rays going from the object, you can predict where the image will be and where the image would look like.

12. Virtual Image
Virtual Image- an image formed by rays that appear to be coming from a certain position, but are not actually coming from this position
image does not form a visible projection on a screen
brain assumes that a light ray travels in a straight line
note the lateral inversion all images in plane mirrors are reversed

13. Let’s use the power of Reflection on Abraham Lincoln’s face 

14. Abraham Lincoln
Left side face

15. Abraham Lincoln
“Left side” face
“Right side” face

16. Four Characteristics of an Image
L.O.S.T
1. Location
closer than, farther than, or the same distance as the object to the mirror
2. Orientation
upright or inverted
3. Size
same size, larger than, or smaller than the object
4. Type
real or virtual image

17. Characteristics of an Image in a Plane Mirror
1. Location
the same distance as the object to the mirror
2. Orientation
upright
3. Size
same size
4. Type
virtual image
You can predict these characteristics by drawing a ray diagram

18. Location Image is located on the same side of the mirror
Image is located on the opposite side of the mirror
Image can also be located at a specific point (e.g. at centre of curvature, f<di<2f, etc.)
Note: image location will always be di=do for plane mirrors

19. Orientation MIRROR MIRROR MIRROR MIRROR
a) Upright - image is right-side up
b) Inverted - image is upside-down
c) Laterally Inverted - image is flipped horizontally a)
MIRROR b)
MIRROR
MIRROR c)
MIRROR

20. Size a) Enlarged - image is larger than the object
b) Reduced - image is smaller than the object
c) Same - image is the same size as the object a) b) c)

21. Type
Real - image appears in front of the mirror (could be projected onto a screen)
Virtual - image appears behind the mirror

22. Locating an Image in a Plane Mirror Using a Ray Diagram Page 416

23. Locating an Image in a Plane Mirror Using a Ray Diagram

24. Locating an Image in a Plane Mirror Using a Ray Diagram

25. Locating an Image in a Plane Mirror Using a Ray Diagram

26. Locating an Image in a Plane Mirror Using a Ray Diagram

27. Reflection and Stealth Technology
The shape of and surface paint on the stealth aircraft absorbs and reflects radar waves so that only a few of the waves reach the ground radar station. This renders the aircraft virtually invisible.

28.  Homework  Read Section 10.2 on Pages 411-416
Complete # 1-4, 6 found on Page 418.