Light - Reflection - Illusion
 
George Brydie                  Edward White School
                               1136 W. 122nd St.
                               Chicago IL 60643
                               (312) 535-5671
Objectives:

    1. The student will understand The Law of Reflection in practical 
application as it applies to a plane mirror. 
    2. The student will understand that a distance of an object in front of a 
mirror is equal to the distance of that object behind the mirror. 

Class Strategy:

    - Introduce lesson with Phenomenological Floatation Illusion and Magic Box 
      trick
    - Students investigate five stations which illustrates the Law of Reflection 
    - Group analysis of data with explanation and use of overhead
    - Group Activity - Making of magic box

Floatation Illusion
     Material--Mirror 36" x 52" --chair--curtain
Discuss with the students about floating like Michael Jordon -- Inform them you 
have mastered the art of floatation.  Stand on chair, jump down over mirror 
(straddle it).  Remember that you are perpendicular to the audience.  Have the 
assistants pull back the curtain.  Lift your leg closest the students.  To them 
it will seems as if you are floating but what you are doing is standing on the 
leg behind the mirror.  Float for a few seconds-let yourself down- have 
assistants close curtain. 

Magic Box Illusion
     Material--Box 18" x 24" x 10" with top--contact paper to cover the box--
cardboard flap which will fit diagonally in the box--Mirror or Metallic 
polyester (enough to cover flap)--Cut window in front of box approximately 15" x 
18". 
Procedure - Attach mirror to flap and place flap diagonally in box - This gives 
the image of an empty box.  Place an object (rabbit) behind flap - Explain to 
your students that the box is empty - put hand inside - remove top - pull out 
rabbit. 

            STATIONS OF INVESTIGATION

Station 1  How High To Place the Mirror

Procedure - Pose the students with the question "How high do I have to hang the 
mirror in order to see all of myself including my shoes?"  Two students hold the 
mirror against the wall - a third student looks at himself in the mirror, and a 
fourth measures the maximum height of the mirror off the floor.  Attach the 
mirror at that height and let all the students see themselves in the mirror. 

Questions to be answered
    1. Does the distance from where you stand to the mirror affect the image of 
yourself in the mirror? 
    2. Would a shorter person have to move the mirror in order to see his feet? 
    3. Can you draw the path of light rays that you see coming from your feet? 

Conclusion
    Because the image of a person is exactly the same distance behind the 
mirror, the height of the mirror to the floor is always 1/2 of the person's 
height (the angle of incident is equal to the angle of reflection.) 

Station 2  Funny Reflections
     Materials--Unframed square or rectangle mirror
Procedure - Write the following words in large even capital letters CHEEK, BIKE, 
DECIDE, BOX, CHICK, CHOKE, BOOK) cut each in half.  Place mirror vertically 
against the paper. 

Questions - Will this work with all printed words?  Which letter, when cut in 
half will appear whole? 

Strategy - The image in the mirror shows that all images are actually found 
behind the mirror. 

Station 3  Look at Yourself as Other See You
     Material--Two square or rectangular mirrors without frames
Procedure - Have one student stand the two mirror perpendicular to each other. 
Student observation. Place mirrors in one plane.  Make Observations. 
Questions - 1. Why did the left hand appear on the right in the perpendicular 
mirror?  2. How do light rays travel from the object to mirror and back to the 
observe's eye?  3. What happened to your image when the mirrors were 
straightened? 
Conclusion - The light ray of the object (which is yourself) are reflected in 90 
degree angles from one mirror to the other and then back to the eye.  In a 
regular straight mirror, the rays bounce right back to the eye. 

Station 4  The Cool Candle Flame
     Materials--Rectangular piece of window glass and two identical candles
Procedure - 1. Mount the glass vertically between bricks or books.  2. Fix one 
candle in front of the glass sheet.  3. Fix the second candle an equal distance 
in back of the glass sheet.  Light only the first candle.  Align the second so 
that the flame of the first seems to be atop the second (if looking from the 
front). 
Questions - 1. Why can you hold your hand above the second candle?  2. What is 
the distance of the first candle to the glass?  What is the distance of the 
second candle to the glass?  Compare the distances. 
Conclusion - This shows that the image of an object in a mirror is located 
behind the mirror, exactly the same distance from the mirror as the object is 
in front of it. 

Station 5  Pong Video Game
    Material--pong Video Game and television
Procedure - Play the game - record the winner
Questions - Who won?  Why?
Strategy - Just as the tennis ball is reflected off a wall-a narrow beam of 
light is reflected from a mirror (the angle of incident is equal to the angle of 
reflection.) 

Note: Patterns for Magic Box may be obtain at The Museum of Science and Industry 
or call me at school and I will send you a copy.