Grade Ten Academic Science
Mr. Findlay

Have a partner hold up a mirror infront of your
shoe laces so that you can see your laces being
reflected.
 Using the reflection in the mirror only, try to tie your
shoes.

Alternately, try writing something on a piece of
paper that can be read correctly in a mirror…
 I.e. try writing: “Grade Ten Academic Science” on a
piece of paper so that someone could read it if it were
held up in front of a mirror.

Mirror Writing: is formed by writing in the direction that is the
reverse of the natural way for a given language, such that the
result is the mirror image of normal writing: it appears normal
when it is reflected in a mirror. It is sometimes used as an
extremely primitive form of cipher. The most common modern
usage of mirror writing can be found on the front of ambulances,
where the word "AMBULANCE" is often written in very large
mirrored text, so that drivers see the word the right way around in
their rear-view mirror—and understand why they hear a loud siren
behind them.
Leonardo da Vinci’s
mirror writing…

When our eyes detect a
reflected light source in a
mirror, our brain actually
projects these light rays
backwards in a straight line.
Which results in our brain
imagining there is a light
source behind the mirror.
 There is of course no light
source behind the mirror
because it is opaque; however
the imaginary light source
behind the mirror is referred
to as the virtual image.

There are many ways to achieve the location
of images in plane mirrors…The most
common practice is the one in which we just
talked about
 Another process to locate images is outlined in
the pages 490-491
 This process uses equal perpendicular lines to
locate the image.
▪ Please refer to figure 8 on page 491…
The distance from the object
to the mirror is exactly the
same as the distance from
the image to the mirror.
 The image line is
perpendicular to the mirror
surface
 The image is upright but
flipped horizontally
compared to the object:
Lateral inversion


When you are looking at an object in a plane
mirror you need to consider the four
following characteristics…
 Size
 Orientation
 Location
 Type

Compared to the object is it the same size,
smaller or larger…

Which way the imaged is oriented compared
to the object: upright or inverted

Is the object the same distance away as the
virtual…?
?
Object
Image

Is this the real image or the virtual image?
O
mirror

Rays from object O become
divergent after reflection.
O
I
mirror
Our brain assumes
light travels in straight
lines. As a result, we
“see” the image of
object being reflected
behind the mirror.
The
reflected
rays
appear to come from I,
which is called a virtual
image. Dashed lines are
used to represent these
virtual rays.
The Big 4: SALT
1. Size  image is same
size/smaller/larger than object
2. Attitude  image is upright or
inverted compared to object
3. Location  distance between mirror
& image compared to distance
between object & mirror
4. Type of Image  virtual vs. real
The Big 4: SALT
1. Size same
2. Attitude  upright
3. Location  same distance
between object & image to
mirror
4. Type of Image  virtual vs.
real
 It is also laterally inverted
(flipped)

The properties of light rays can be
applied to determine the location of a
virtual image

The following observations can be
applied to an object and its virtual image
 Distance from object to mirror = Distance
from image to mirror
 Object-Image line is perpendicular to the
mirror surface
1.
2.
3.
The ray diagram
shows that
•
ON = NI
•
OI⊥MN
N
O
M
I
O
I
A girl can just see her feet at the
bottom edge of the mirror.
150 m
150 m
What is the distance between the girl
and her image in the mirror?
(a) Image distance = Object distance
Total Distance = 150  2 = 300 m
150 m
150 m
150 m
Why can the top eye see the image of the
arrow even though it is below the mirror?
First, find
the image
(quick way)
measure
Same
distance
Now draw
rays to the
eye
The ray hits
the mirror
Now show
where the
ray really
comes from
Can the second eye see the bottom of the arrow?
Draw the
ray from
the arrow
to the eye
The ray
does not hit
the mirror
NO!
1.
2.
Practice Worksheet
Page 493 #1, 3, 4, 5 (c), 6, 7, 9, 11