1. Seeing Things Plane Mirror Image Characteristics

2. Image Characteristics
Try printing your name on a piece of paper so that it can be easily read in a mirror.
This will take some time. The trick is to maximize interest but move on when it becomes just “time off”.

3. If you use the inversion of your name as the object, the image will again be flipped back so that it is easily read in the mirror.

4. The object and image appear to be flipped or folded about the mirror.
Looking from the Side
The distance of points on the object to the mirror is the same as that of corresponding points on the image to the mirror.
The object and image appear to be flipped or folded about the mirror.

5. There is a more useful way of thinking about the image inversions
There is a more useful way of thinking about the image inversions. When the object is between the Eye-Brain and the mirror,
the front edge of the object is flipped to the back edge of the image……..

6. There is a more useful way of thinking about the Image inversions
There is a more useful way of thinking about the Image inversions. When the object is between the Eye-Brain and the mirror,
the front edge of the object is flipped to the back edge of the image
and the back edge of the object……..

7. This is called Front-Back Inversion.
There is a more useful way of thinking about the image inversions. When the object is between the Eye-Brain and the mirror,
the front edge of the object is flipped to the back edge of the image
and the back edge of the object is flipped to the front edge of the image.
This is called Front-Back Inversion.

8. Therefore, the image does not reverse left and right.
In a mirror, the object of a right hand and its image both point to the right.
Therefore, the image does not reverse left and right.
See Framing the Real Thing – right hand is changed to left hand by changing in into out AT THE END OF THIS VIDEO

9. Therefore, the image does not reverse up to down.
In a mirror, the object of a right hand’s thumb and its image both point up.
Therefore, the image does not reverse up to down.
See Framing the Real Thing – right hand is changed to left hand by changing in into out AT THE END OF THIS VIDEO

10. Therefore, the image does change In to Out, or Front to Back.
In a mirror, the object of a right hand pointing in results in an image pointing out.
Therefore, the image does change In to Out, or Front to Back.
See Framing the Real Thing – right hand is changed to left hand by changing in into out AT THE END OF THIS VIDEO

11. BUT, the image of a right hand looks like a left hand.
See Framing the Real Thing – right hand is changed to left hand by changing in into out AT THE END OF THIS VIDEO

12. AMBULANCE OBJECT IMAGE In a plane mirror, RIGHT is changed to LEFT
by changing IN into OUT.

13. Finally, the image in a plane mirror is called VIRTUAL.
We usually see things because rays of light go from what we are looking at straight into our eyes.
This applies to real objects as well.

14. Images.
When light rays enter the Eye-Brain, it cannot tell where they actually come from.

15. Images
When light rays enter the Eye-Brain, it cannot tell where they actually come from.
The image only appears to be behind the mirror because of the way light reflects off the mirror.

16. A plain mirror can be treated like a window.
The image is seen through this “window”.

17. Of course, mirrors are not windows. Mirrors are opaque
Of course, mirrors are not windows. Mirrors are opaque. The only light rays that exist are those that reflect off the mirror.
This is why images in plane mirrors are called VIRTUAL.

18. Review
Images in plane mirrors have the following characteristics:
They are the same size as the object.
They are Inverted Front to Back which makes them appear to be left/right or top/bottom inverted.
They are located an equal distance from the mirror as the object is and the line connecting the object and image intersects the mirror at 90 °.
They are virtual.

19. Size Same Review in Table Form
SILT - Image Characteristics Review Table
Size
Same
Inversion
Front to Back
Location
Equal to Object Distance, 90º Behind Mirror
Type
Virtual

20. REMEMBER SILT (OR SALT)
Inversion/Attitude

21. REMEMBER SILT (OR SALT)
We use 4 main characteristics to describe an image.
Size of an image compared to the object (Ex. Same Size, Smaller, Larger)

22. REMEMBER SILT (OR SALT)
Inversion (Attitude) of Image
– which way the image is oriented compared to the object: Upright or Inverted (Upside down)
Inversion/Attitude

23. REMEMBER SILT (OR SALT)
Location of Image
-in front/behind a mirror or lens
-distance from mirror or lens compared to object distance

24. REMEMBER SILT (OR SALT)
Type of Image (Real or Virtual)
– Real being an image formed when light is actually arriving at the image location (Think of movie projectors).
-Virtual being something that looks beyond the mirror (Think of when you see your reflection).

25. Does a candle have to be in front of a mirror in order to form an image?

26. It is there, but how must you look?
Does a candle have to be in front of a mirror in order to form an image?
Both candles can form images. The “mirror” must be extended to find the location of the image for candle #2.
It is there, but how must you look?

27. Can all Eye-Brain observers see all images??
a) Show where the images are located.

28. Show where the images are located.
Both candles can form an image. The mirror must be extended to find the location of image #2.

29. i. Which Eye-Brain can see the image of candle #1?
C) D) & E) can see image #1. The mirror acts like a window. A straight line must exist between the Eye-Brain and image through the mirror.

30. ii. Which Eye-Brain can see the image of candle #2?
A) B) C) & D) can see image #2. The mirror acts like a window. A straight line must exist between the Eye-Brain and image through the mirror.

31. Use the Applet described in the notes to review further.
What determines whether an Eye-Brain observer can see an image or not?
Mirrors act like windows. A straight line through the mirror must exist between the Eye-Brain and image.
For a free applet to further explain the answers to questions 2-5, go to NTNUJAVA Virtual Physics Laboratory Registered users (free) will be able to get files for offline use. Once you have done this, search for “Image formed by plane mirror”. Once you have downloaded, the file name is “mirror_e.html” .
Use the Applet described in the notes to review further.