Applied Science - Science and Math (4B) Post Lab
 OBJECTIVES: Exploring optical illusions. Designing an experiment. VOCABULARY: optical illusions perception qualitative quantitative MATERIALS:  worksheet Students collect data on how people perceive optical illusions.
BACKGROUND:

Optical illusions are caused when  shapes and light interact with our sense of sight and make our brain interpret objects that may not be there.  There are different types of optical illusions from camouflage to mirages.  Camouflage refers to when objects, either two-dimensional or three-dimensional,  blend into one another.  Warriors and hunters have used this illusion to hide from their enemy or catch their prey.   A mirage is when a deceptive appearance of objects is caused by refraction (bending of light) in layers of air of varying densities.  Many magicians use this principle to help deceive our eyes.

Students will be looking at a visual illusion caused by geometric placement where shading, shape, and color confuse our sense of sight into seeing something two different ways from the same picture.  Sometimes you train your eyes to look one way and you see one object, and then look another way and see another object.

PROCEDURE:

1. Experiments conducted by scientists are usually designed before data is collected.  Data can be collected on just about anything as long as the data can be compared and contrasted.  Ask students how they would design an experiment using optical illusions.

2. Explain that an optical illusion appears to be something that it isn't.  That sounds "qualitative," or a least subjective.  How can it be made quantitative?  Compare girls and boys reactions and see if there is a pattern.  Ask students if there is any other way.  If they don't come up with a better experiment, use the suggestion below.

3. Show the optical illusions to the class of the mouse/man and vase/2 faces,  and have them write down what they see.

4. Review what they saw and point out the possibilities of each picture.  Record the data on the board. Subdivide their answers into girls and boys.

5. After going through the pictures, see if students' results can be made quantitative by putting numbers on the data.  You can quantitate the results by collecting data that looks at groups of people by sex (in this case).  Have students construct a bar graph.  Collect the data from the class  using the following format.  Students will have to think how to construct such a graph because it has more variables than the previous exercise.
 BOYS GIRLS mouse old man vase 2 faces
1. Below is a possible way in which students can graph the data. Notice this type of bar graph compares boys and girls. Discuss with students if you can interpret the data using the graph generated.