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  This process uses equal perpendicular lines to locate the image. ▪ Please refer to figure 8 on page 491…

 Rays from object O become divergent after reflection. mirror O

Our brain assumes light travels in straight lines. As a result, we “see” the image of object being reflected behind the mirror. mirror O I The reflected rays appear to come from I, which is called a virtual image. Dashed lines are used to represent these virtual rays.

 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?

The Big 4: SALT 1. S ize  image is same size/smaller/larger than object 2. A ttitude  image is upright or inverted compared to object 3. L ocation  distance between mirror & image compared to distance between object & mirror 4. T ype of Image  virtual vs. real

The Big 4: SALT 1. S ize  same 2. A ttitude  upright 3. L ocation  same distance between object & image to mirror 4. T ype 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

OI ⊥ MN N M ON = NI OI The ray diagram shows that

O I

Example 2 A girl can just see her feet at the bottom edge of the mirror. 150 m 150 cm What is the distance between the girl and her image in the mirror?

Example 2 cont’d… (a) Image distance =  Total Distance = 150  2 = 300 m Object distance 150 m 150cm 150 m

Example 3a) Why can the top eye see the image of the arrow even though it is below the mirror? First, find the image (quick way) Now draw rays to the eye Now show where the ray really comes from measure Same distance The ray hits the mirror

Example 3b) 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. Practice Worksheet 2. Page 493 #1, 3, 4, 5, 6, 7, 9, 11