Optical Illusions for a School Science Project: Choosing a Topic, Running the Experiment and Writing It Up

Why optical illusions make a good science project

An optical illusion is when what you see differs from the actual shape, colour or movement. It doesn't happen because of poor eyesight; given the right conditions, it happens in much the same way to almost everyone. This "happens to everyone" quality is what makes it a good match for a science project.

• You need almost no equipment: you can start with a screen and some paper, at no cost for materials.
• Conditions are easy to change: the factors you can vary, such as staring time, colour strength and screen brightness, are clear.
• You can show the results to others: if family or friends try it under the same conditions, that becomes data straight away.
• There isn't just one answer: some people see it and some don't, so material for your discussion builds up naturally.

Rephrase your topic as a comparison

When choosing a topic, rephrase "find out about optical illusions" as "how does △△ change when I change ◯◯?". In this form, what you need to measure is decided automatically.

• Change only one condition (the cause). If you change time and colour at the same time, you can't tell which one made the difference.
• Decide what you'll measure (the result) first. Even a simple "saw it / didn't see it" is perfectly good data.
• Write down your prediction first. It's fine if it's wrong; being wrong is itself material for your discussion.

Steps for comparing conditions with an afterimage illusion

If you stare at a colour-inverted image for a while and then switch to a black-and-white image, the picture that should be black and white appears to have colour. This "negative afterimage" is good for comparing different staring times and colour strengths.

1. 1

   Make your record sheet first

   Before starting the experiment, prepare a table on paper for writing down conditions and results. If you write them up later from memory, the details get fuzzy.

2. 2

   Try once with the baseline condition

   In the Color Afterimage Illusion tool, set the staring time to 30 seconds and wait without taking your eyes off the mark in the centre. When it switches to black and white, record which colours you saw where, and for roughly how many seconds.

3. 3

   Repeat, changing only the time

   Change the setting to 10, 20 and 45 seconds and repeat the same steps. Don't change any other conditions (screen brightness, where you sit, room lighting).

4. 4

   Rest your eyes before the next run

   After each run, close your eyes or look into the distance for about 30 seconds. If you go straight on, the previous afterimage lingers and the results get mixed up.

5. 5

   Have other people try it under the same conditions

   Ask family or friends to try it with the same settings on the same screen. Three to five people are enough to see a trend. Remember not to pressure anyone, and tell them they can stop at any time.

How to make a record sheet

Record your results in a form that's easy to turn into tables and graphs later. If you prepare columns like the ones below, you can paste the sheet straight into your report.

• Besides "saw it / didn't", include at least one item you can express as a number, such as how many seconds it lasted, so you can make a graph.
• The notes column pays off later when you write your discussion. Write things down even if they seem trivial.
• Keep the runs that didn't work rather than deleting them. Knowing which conditions failed is a result in itself.
• Saving the afterimage images themselves gives you figures for your report. The tool lets you save the inverted image.

A template for writing it up

Science reports are easiest to write in the following order. Whether it's one poster or a few pages in a notebook, the order is the same.

1. 1

   Motivation

   Write 2 or 3 lines on why you chose this topic. "Because I was amazed that a black-and-white photo looked coloured" is enough.

2. 2

   Prediction

   Write what you thought before the experiment, in a form you can compare with the results, such as "I thought the longer I stared, the longer the afterimage would last".

3. 3

   Method

   Write the equipment, conditions and steps you used in enough detail that a reader could do the same thing. Being specific here makes a big difference to how it's judged.

4. 4

   Results

   Include the record sheet as it is, and make graphs of anything you can express as numbers. Write only the facts here, not the reasons.

5. 5

   Discussion

   Compare your prediction with the results and explain in your own words why things turned out that way. Link explanations such as "if you keep looking at the same colour, the parts of the eye that respond to it get tired" with what you looked up.

6. 6

   Reflections and sources

   Write what you learned by doing it and what you'd like to investigate next. Record the names of the books and websites you used.

If you get stuck on the discussion, list things under three headings: "what matched my prediction", "what was different" and "where people differed", and it will start to take the shape of sentences. Even if you can't say for certain why differences appeared, listing possible causes is fine.

Ideas for taking it further, and safety notes

• Make illusion images from your own photos: create inverted images from pictures you have, and compare which kinds of photo work well for afterimages. Pictures with clearly separated colours give stronger effects.
• Grid coarseness and recognition: with the pixel art tool, make the same picture at 8, 16 and 32 squares, and ask people at which size they can tell what it is.
• Compare with black-and-white illusions: organise how afterimage illusions differ from illusions that don't use colour (illusions of line length or brightness).
• Measure again after some time: have the same person try on different days to see whether health or time of day makes a difference.

Flashing images can affect some people's health depending on their constitution. Avoid experiments that use flashing, and stick to switching between still images. If you're doing it with small children, an adult must always be there to supervise.

FAQ

How many days does an optical illusion science project take?

An experiment that compares changed conditions can be finished in one day. The experiment itself takes about 30 minutes, and making the record sheet and writing up the report about 2 to 3 hours. If you include a follow-up that has the same people try again on another day, plan it over two days or more. Preparing the record sheet before the experiment shortens the work on the day.

What kind of topic makes it feel like a real science project?

Instead of "find out about optical illusions", include the condition you'll change and what you'll measure in the topic, as in "how does the afterimage change when I change the staring time?". Change only one condition, and record results in a form such as "saw it / didn't" or "how many seconds it lasted". Writing your prediction first makes the discussion easier to write.

What should I do if I can't see the afterimage properly?

Switch to a longer staring time, and keep looking at the same spot for a few seconds after it switches. Moving your eyes makes the afterimage shift and disappear. Turning up the screen brightness, not making the room too dark and not sitting too close to the screen also help. Not seeing it well is a result too, so record it along with the conditions.

Is there anything to be careful about in the experiment?

Don't keep staring for a long time. Keep each run to about 45 seconds at most, with time to rest your eyes in between. Stop immediately if you feel eye pain, a headache or nausea. When others help, don't pressure them, and tell them beforehand that they can stop at any time. Don't use flashing images; switch between still images instead.