1. Ray Diagrams & Reflection Images in plane mirrors

2. Ray Diagrams Light travels in a straight line
A light ray is represented by a straight line and an arrow showing the direction and ‘straight-line’ path of light

3. Normal
Incident ray
Reflected ray

5. Reflection Reflection is light bouncing back from any surface
Specular reflection is reflection of light off a smooth surface
A mirror is any polished surface that exhibits reflection
Diffuse reflection is reflection of light off a surface that is not smooth

6. Specular
Reflection
Diffuse
Reflection

7. The Laws of Reflection incoming ray that hits the surface
line at right angle
to mirror surface
ray that bounced
off the surface

8. The Laws of Reflection incoming ray that hits the surface
angle between incident ray
and the normal
angle between
reflected ray
and the normal
line at right angle
to mirror surface
ray that bounced
off the surface

9. Laws of Reflection The angle of incidence equals
the angle of reflection
i = r
2. The incident ray,
the reflected ray,
and the normal
all lie in the same plane

10. Using Light Rays to Locate an Image
Light rays and the laws of reflection help determine how and where an image is formed in a plane mirror.

11. We all know that light travels in a straight line.
When your eyes detect reflected light from plane mirrors, your brain projects the light rays back in a straight line.

12. Finding the Image light source normal mirror apparent light source
distance
of object
from mirror
normal
mirror
apparent
distance
of object
from mirror
object-image
line
apparent
light source
Distance from object to mirror = distance from image to mirror.
The image appears to be the same distance behind the mirror as the object is in front of the mirror.
2. Object-image line is perpendicular to the mirror.

13. Types of Images
Real Images- mirrors can produce images that can be projected on a screen. A real image is ALWAYS inverted and appears in front of the mirror.

14. Virtual Image- mirrors can also produce images that cannot be projected on a screen. A virtual image is ALWAYS upright and appears behind the mirror.

15. Virtual Images in Plane Mirrors
Optics: Reflection, Refraction
                                    
Virtual Images in Plane Mirrors
05/25/2006
   
"Virtually":  the same as
If light energy doesn't flow from the image, the image is "virtual".
Rays seem to come from behind the mirror, but, of course, they don't.  It is virtually as if the rays were coming from behind the mirror.
As far as the eye-brain system is concerned, the effect is the same as would occur if the mirror were absent and the chess piece were actually located at the spot labeled "virtual image".
Lecture 16

17. Reflection of Light Source

18. Reflection of an Object

19. Finding the Image with Rays
In a plane mirror the image is:
virtual (the light rays do not really converge, our brains just think they do.
the same size as the object.
the same distance behind the mirror as the object is in front.
laterally inverted (right becomes left)
upright

20. Locating images in a Plane Mirror
reflected
mirror
incident
object
Image of object

21. Ray Diagram Using 2 Points:
Perpendicular ray
Reflected
ray
Incident ray

22. Locating Images in a Plane Mirror
Is there any easier way?
Of course...
Draw line & measure
Repeat lines behind mirror
2cm
2cm
object
3.5cm
3.5cm
mirror

23. Image Formation in Plane Mirrors

24. Locating Images in a Plane Mirror
From top of object, draw a line perpendicular to mirror (along normal)
measure the distance of this line and extend the line, the same distance, behind the mirror
repeat this step from the bottom of the object
for complicated objects, draw more than two lines
2 cm
3.2 cm
2 cm

25. S.A.L.T SALT is used to describe images formed by mirrors.
S- Size: compared to original object is it same size, smaller or bigger?
A- Attitude: which way the image is oriented compared to the original object (upright or inverted).
L- Location: location of the image (in front or behind the mirror).
T- Type: is the image a real image or virtual image?

26. PLANE MIRRORS Characteristics of a plane mirror image:
Object size= Image Size
Object distance from mirror= image distance from mirror
Attitude (orientation) is ALWAYS upright
ALWAYS forms a virtual image
Image is reversed- left to right