Journal #81
April 22, 2011
You do not need to copy this paragraph

Use the concave and convex mirrors
on your table. Start with the mirror
very close to your eye and slowly
back it away. Describe the changes
to your image until the mirror is a full
arm’s length away
Answer to Journal #81
Concave: The image starts off very close to
regular size and increases in size. Image
becomes completely blurred. Image reforms
and is inverted and enlarged. It becomes
reduced the farther away you move beyond
this point.
 Convex: The image starts off very close to
regular size but reduces as the mirror is
pushed back. Also, image is not a true
representation of object… slightly skewed.

Plane Mirror
Reflection is
on top of
incident light
Image formed is:
Virtual
Upright
Same Size
Try to fill in this chart from
memory… best way to study!
Object
Placement/Mirror
Plane Mirror
B/n Concave
Mirror and FP
At FP of Concave
Mirror
B/n FP and CC of
Concave Mirror
At CC of Concave
Mirror
Beyond CC of
Concave Mirror
Convex Mirror
Real or Virtual
Upright or
Inverted
Size of image
compared to size
of object
Answer Key to Table
Object
Placement/Mirror
Real or Virtual
Upright or Inverted
Size of image
compared to size
of object
Plane Mirror
Virtual
Upright
Same
B/n Concave
Mirror and FP
Virtual
Upright
Enlarged
At FP of Concave
Mirror
No Image
No Image
No Image
B/n FP and CC of
Concave Mirror
Real
Inverted
Enlarged
At CC of Concave
Mirror
Real
Inverted
Same
Beyond CC of
Concave Mirror
Real
Inverted
Reduced
Convex Mirror
Virtual
Upright
Reduced
How to make a study game
Take 4 sheets of blank paper and fold them in
half 3 times to create 8 equal sized sections
Cut each of the rectangular shapes made by
the creases
How to make a study game
Lay out the individual rectangles in a 4 by 8 grid
How to make a study game
Remove the bottom row and save them as extras (in
case you make a mistake)
How to make a study game
In the first column, write each of the seven possible
situations for mirrors AND/OR draw the set up
How to make a study game
On the back of those same cards, write IN PENCIL
the answers for that card
How to make a study game
In the other columns, write the three answers each
on a separate card for the situation on the left
How to PLAY a study game
Collect all of the answer cards in a single stack and
all of your setup cards in a different stack
How to PLAY a study game
Shuffle both stacks, then deal out the setup cards in
random order
How to PLAY a study game
Place all of the answer cards on the table
Turn over the setup cards and check your answers!
Journal #82 April 25, 2011
WITHOUT USING YOUR NOTEBOOK!!!
If you know the focal length of a
concave mirror, where should you
place an object so that its image is
upright and larger compared to the
object?
 Will this produce a real or virtual
image?

Journal #82
Answer
Place the object between the focal
point and the mirror.
 The image will be virtual

Lens/Mirror Equation




(units of length MUST
match)
f stands for focal length
di is the distance from
the mirror/lens to the
image
from
do is the distance
the mirror/lens to the
object

1
i
1 1
o
di  ( f
1
1 1
o
do  ( f
1
f  (d  d )
d )
1 1
i
d )
Image Height

Magnification of an image can be
found by a series of ratios between
the distances of objects and their
images and their respective heights
as shown below.
hi di

ho
do
Helpful Hints for Mirror Probs

In the formula, the numbers can tell you the
characteristics of the image:

Size
• Reduced ( |hi| < ho )
• Same Size ( |hi| = ho )
• Enlarged ( |hi| > ho )

Orientation
• Upright (hi positive)
• Inverted (hi negative)

•Focal point for concave
mirror is always positive.
•Focal point for convex
mirror is always negative.
Type of Image
• Real (di positive, in front of mirror)
• Virtual (di negative, behind the mirror)
Example problem 1

A concave mirror has a radius of
28cm. An 15cm tall object is placed
25cm from the mirror. Describe the
image formed. What will be the height
and position of the image?
Example problem 2

A convex mirror has a focal length of
32cm. An 17cm tall object is placed
1.0m from the mirror. Describe the
image formed. What will be the height
and position of the image?
HW Problems
P. 469 13-16
 P. 472 17-21

P. 469
P. 472
Spherical Aberration
Special Note:
 Parallel light rays that are far from the
principal axis are not reflected by spherical
mirrors to converge at the focal point. This
defect is called spherical aberration. To
avoid this dilemma, spherical mirrors have
been replaced with parabolic mirrors in
devices such as telescopes that require
extreme accuracy and focus.