Sunday, October 2, 2011

Science sunday – oct. 3, 2011

Light and Colors and How Our Eyes See Them

color paddles, flashlights - ready to explore how light works!

Last winter we made a very cool pinhole camera that helped us understand how light enters our eyes and helps us see.  This week we did some more activities in relation to this idea.  This time we added colors into the mix.

Lesson: Light bounces off of objects and into our eyes, while absorbing some colors and reflecting others.  White light is made up of all the colors of the rainbow, hence we see the colors of light that are reflected from objects, and the other colors of light are absorbed by those objects. 

Got that?

Really this is a pretty complicated concept to grasp (at least for me!), so these activities were mostly just for fun, and to give M’s 5 year old mind something new to grapple with.  {He is a mind-grappling sort of boy, and never happier than when he is trying to understand how something works. ;) }

We began by talking about the cones we have in our eyes.  These are little cone-shaped cells; some of them respond to red light (and tell our brain we see red), some respond to blue light, and some to green light.  M had to get a magnifying glass at this point to see if he could find the cones in my eyes.  He couldn’t and he is feeling a bit skeptical about the whole thing still. ;)

First experiment:

red and blue circles on white paper

I drew a red circle on a piece of white paper and we stared at it for about a minute, trying hard to focus only on it.  After a while we looked away and stared at just the white paper.  We could see a “spot” on the white paper that looked greenish-blue.  Why does this happen?  Well, the red cones get tired of looking at all that red for so long and  take a break when we look away; the green and blue cones are still working and so instead of seeing white, we see white minus the red, and end up with a greenish-blue spot.  M thought this was a bit like magic. :)  That’s a much easier explanation, isn’t it?


Second experiment:

After looking at a blue circle, looking away made us see yellow.  Yellow is what red and green light mixed together make.  M was pretty amazed that they didn’t make brown, because (he knows from experience) that red and green paint would make brown.  We talked about how we would eventually get black if we mixed all the colors of paint together, but if you have all the colors of light (a rainbow) mixed together you would not get black, you would get white.  How could it be pitch black with all that light shining?  Black is the absence of any light

We used our color paddles (pictured at the top of this post) and two flashlights.  I think we should have been in a darkened room for this to work correctly… and we will have to do it again some time.  We tried mixing red and green light by holding the red paddle over one flashlight and the green paddle over the other flashlight and then shining them both onto the refrigerator.  We saw this:

mixed colored lightsMaybe there is a tiny spot of yellow in the middle there?

Then we tried mixing red, green, and blue together (should have given us white) and got this:mixed colored lights (2) 

Ah, well.  Interest was waning at this point so we moved on… (really, I think this was supposed to have been done in a dark room; if you try it and it really works, let me know!).


Third experiment:

sectioned circles and markers

For fun, we decided to color some circles and see how they looked while spinning.  We have a handy-dandy little set of Snap Circuits that includes a motor and a plastic fan.  We simply taped our colored circles onto the fan and flipped the switch to watch them spin.  You can do the same thing by following these directions at to spin your circles with string.

Here are the designs we went with, and how they looked while spinning…

Red, blue, and yellow:spinning primary colors

Red, blue, yellow, purple, green, orange:spinning primary and secondary colors

Silly pictures:spinning silly drawings

Actually, the first two did not look quite so “stripey” as they look in these photos.  They were more like the bottom one, but more solid. 

I am linking this up to Science Sunday, check out the other science activities there!

Science Sunday

Have a beautiful day! :)

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