Kids Science Project
 

My eight year old daughter has her first real science project due. The teacher let the kids figure out what they would be working on with some guidance. My daughter has decided to figure out whether different colors absorb different amounts of light. How do I help her create an accurate experiment? I was thinking that maybe we could mount a spot light over several different color pieces of construction paper and monitor temperature changes with an infrared pyrometer. I hate this because I am not trying to do the project for her but I'm not really sure how to lead her to creating an accurate way to test her hypothesis with it still being her idea. Any ideas would be greatly appreciated!

-Shawn

I think your idea of using the infrared pyrometer is a good one. An alternative idea is to try to create a crude radiometer and time the rpm from color to color.

Shine light on X stacked sheets of red colored cellophane/plastic sheet (probably can get at office supply or art supply store). Increase X from 1 to N(red) until no more light visible through paper. Repeat with same weight cellophane of other colors, record N(blue), N(green), etc. Compare N values. Control intensity of light source by placing a pinhole between light and cellophane stack - so you don't end up with a 100w bulb and $30 of cellophane for each color . . .

Another way would be to build a long cardboard box w/ light bulb at one end, then a series of baffles such that light has to reflect past each baffle to get to the next, other end closed. Pinhole above each baffle so that you can peer in and see if that baffle is illuminated. One side of box opens so that you can reach in and line the baffles w/ colored paper. Line all baffles w/ red paper, what is the last baffle illuminated, repeat for other colors. Also try "glossy" versus "matte" paper.

These might measure slightly different things, might be interesting to see if they agree.

Also interesting to see if you can detect the difference between different light sources - e.g. can you determine a diffierence between an incandescent bulb's color profile vs a daylight CFL vs a white LED, from the ratio of the various N's measured for each light source?

Ideally best to do a kid's science experiment w/o complicated test & measurement equipment.

Edit: Here is something that also looks fun, and more fun if replace the ammeter w/ a motor and spinning propellor, then count the rev/min. Or have the motor drive a pulley that lifts a weight and measure time to lift.

http://www.makeitsolar.com/science-fair-ideas/03-wavelength-light.htm

Thing about the pyrometer is that will measure the transmission of infrared, not visible.

Thanks for the great ideas!

I am afraid that any experiment will be inconclusive, because the amount of light emited by all sources you have access to varies with wavelength. So you will see that the amount of light absorbed by various colors varies, but you will never know for sure if it is because the absorption coeffcient of the color is different or because the amount of light emitted at the wavelength the color absorbs is different than for another color.

Get a light meter (like for photography) and measure the reflected light off the colors.

Show this to your Daughter. Not much to do with her science project but still pretty cool...

http://forums.pelicanparts.com/uploa...1264714807.jpg

That is the exact type of issues that I'm afraid of. Fortunately her teacher is cool and he is more concerned with the students experimenting and being interested in learning than producing the most accurate results. I figure that we will conduct a couple different experiments using the ideas that everyone has given me in this thread and compare the results.

Thanks,
Shawn

Thanks! She will definitely find this interesting.

Unfortunately everyone I know that is into photography enough to have a light meter do not live close to me. Are light meters expensive?

Thanks,
Shawn

I did this exact same science project in about 1981. I used four or five of those cheap aluminum condiment shakers, spray painted each one a different color, put a heat lamp in the middle of of a board, equidistant from them all, filled each with water and put cheap thermometers in each one. It was very crude, but painfully obvious what was going on. I think I got an honorable mention. The year before I built a periscope. Back then, they really judged you on how well you wrote up the explanation, not how elaborate your project was.

edit: ooops, just noticed you meant how each color absorbs light. I did mine on conducting heat.

I am really happy with her teacher this year because he seems more concerned with the students learning and taking an interest in what they are learning about then whether or not the kid (or in a lot of cases parents) put together a flashy project. I think as part of the fun I am going to have my daughter read this thread and decide on her own what idea she would like to use to test her hypothesis.

Thanks,
Shawn

Eight?

Put different color fabrics on the snow outside on a sunny day and time the melting.

Oops. San Diego.


So, do same size ice cubes with maybe different color food coloring? Different color fabrics or something like that...

Keep is simple, not light meters and pyrometers. At least she'll understand what's going on.

Okay so maybe I was using her experiment as an excuse to get an infrared pyrometer;)

I've been trying to figure out something that we could do without having to rely on it being sunny because the weather has been really crazy down here right now (it even rained!!). I guess we could do the ice cube experiment under a spot light if necessary.

No matter what experiment we do I am only going to help her. I am young enough to remember how much it would irritate me when a fourth grader would somehow build a diorama with motorized dinosaurs, working volcanoes, etc.

Light meters such as used in photography have varying sensitivity to different wavelengths of light. That is because they are based on small PV cells and PV silicon has varying sensitivity by wavelength.

It doesn't matter for most photography since the light source is sun or flash or light bulb which are emitting all of the visible spectrum as well as non-visible spectrum too (e.g. infrared and ultraviolet), and whatever is reducing the light level (shadows, usually) is reducing all wavelengths of light more or less equally - "more or less" being in the very crude context of photography where you're only trying to get within an f-stop or so (1 f-stop more = 2X the light level), not exactly high precision.

The human eye also has varying sensitivity to different wavelengths and it even varies between humans.

So, as Aurel says, it's probably not so easy to measure this "precisely". But so what, this is just a kid's experiment. Define "light" as "sunlight at high noon cloudless sky at my house this month", and "brightness" as "brightness as perceived by my eyes", and experiment away!

wavelengths of different colors of light
What Wavelength Goes With a Color?

spectral sensitivity of a (typical? dunno) light meter (scroll to #6)
http://www.dataloggerstore.com/crm_uploads/1336.pdf

stuff on Wratten color filters
http://www.olympusmicro.com/primer/lightandcolor/filter.html

If and when you want to get more fancy w/ light experiments, you can probably rig up cool stuff using photographic equipment. Any old-time used camera store or flea/junk store will yield a $5 camera lens that has a manual aperture and actuating pin, you can use that to reduce the amount of light that is transmitted through the lens in a more or less calibrated way. A slit in cardboard, and a prism bought cheap from an education supply store will separate that beam of white light into colors. A good photography store will also have color filters (sometimes called Wratten filters) that are calibrated to transmit X % of light of a specific wavelength, glass ones cost a bit but gel ones are pretty cheap. Fun stuff like that.

Here is an idea: buy a little solar cell at radioshack, and a set of colored slides. Put each slide in front of the cell, and measure the current of the cell for each color, using a light bulb as source. Look for a the wavelength corresponding to each color online (rainbow chart). Then plot current vs wavelength. If you want to show that absorption varies with wavelength, repeat same experiment with 2 and 3 layers of each slide.

This is a lot of great information and ideas! I think I am probably going to steer her towards one of the ideas that Rick Lee, JYL, or Tcar came up with just because I think those will be the easiest for her to do and understand without this becoming my science project.

Thanks,
Shawn