Sight

Objective:

The objective of this lab is to learn about the amazing sense of sight and how we see colors

Background on

In our society we love to capture moments by taking pictures and looking back at them over time. Now think about your eyes, do you think that your eyes act like a camera? The simple answer is yes. Our eyes have a lens. The lens on a camera just like our eyes allows light into the housing or body of the camera. The lens directs how the light goes in our eyes pointing the light to the back and center of the eye.

Light, although made of waves, does not bend (this is ignoring Snell’s Law, where light bends and refracts in mediums such as water or reflective materials) so when light from an object hits the lens of the eye it continues in a straight line. Since the back of the eye is much smaller than most things that you look at the focal point in the eye will be right at the back of the eye. This creates an upside-down image in the back of the eye. 

But wait, then why do we not see everything upside-down? The answer is our brain acts like the software in the camera and processes the images that we are seeing. A camera takes all the different points of light at the back of the housing and organizes those points into an upright picture. If the focus was off the image will be blurry and if the focus is good the image will be crisp and clear. For most people we have an automatic focus in our eyes so we can switch from looking far away to looking at the small words in a book in front of us. When we have trouble adjusting our focus we use artificial lenses such as glasses or contacts to help us focus objects that are far away or close at hand that we have trouble seeing.

Cameras can also have filters to help deal with different types of light. These filters have to be put on and taken off as needed. We have an auto-adjusting light filter in our eyes called the pupil. This controls how much light we let into our eye at a given time. Our pupils will dilate (open wider) when it is dark out to let in as much light as possible to make it easier to see and will contract when it is sunny out to limit how much light is coming in.

Cameras can see and make out differences in color, for the most part we can as well, but have various limitations with our ability to see colors. For people we can see in black white and shades of gray to a full and varied color pallet and every variation in between. The gene for being able to see color is found on the X chromosome. People who are color blind have a double (for women) or single (for men who only have one X) recessive gene on the X chromosome.

Materials

• Fabric (in as many colors as possible) cut into 6x6 squares

Method

Prepare Experiment

1. Provide all the kids with all the different colors
• Make sure all the squares are given in the same order

Run Experiment

1. Hold up the first square for everyone to see and let them identify what color they think it is
2. Collect the data and write it up on the board
3. Allow for 2-4 main answers and have another category for the kid’s random answers
4. Repeat with the next color square
5. Continue until you have gone through all of the different color squares that you have

Analyze Data

Look at all the data and show how for even for basic colors such as white and black you will see a bit of variation between the kids. When you get into colors like red and green you will see some of the kids having trouble differentiating them because of red-green color blindness.

Conclusions

Your eyes are amazing and provide you with an extraordinary sense, the sense of sight. Being able to see we can observe and change the world around us. We can use our eyes to help see danger and keep us safe. We can use our eyes to figure out how far away something is. We can also use our eyes to learn by reading or seeing different things.

Make It Your Own

Try putting together different color squares where one color is 90 degrees turned from the other and set on top of it. Then look and see what you see. Do you see a mixing of colors where the edges meet up? Can you find combinations that trick your eyes to make different secondary colors?

Extension Activities to do at home

When you get home grab things that are all the different primary and secondary colors (make sure you get your parents’ permission first). Repeat the experiment at home and see how between family members you can still have great differences in what people see.