Science Buddies: "Ask an Expert"

I became interested in light pollution when I was looking for science fair ideas relating to sea turtles. Since lighting can affect nesting sea turtles and hatchlings, I thought I could do something about good/bad lighting.

My proposal right now is which type of light bulb produces the least amount of lux/luminous emittance, and we were going to measure lux of different light bulbs. Independent variable is type of light bulb. Dependent is lux level. LED, CFL, halogen incandescent and regular incandenscent. and I thought i would use bulbs of equivalent watts. like led with 20 watts was comparable to 100 watt incandescent.

Then i was going to measure lux of each in a dark room from the same distance, etc.

To relate it to sea turtles and lighting, i also wanted to look at what happens when you shield the light (which would reduce sky glow and direct the light) but that would be another variable and another type of experiment.

I think this is a very basic project and wanted to do something that wasn't as simple. When i was researching what my experiment could be, I saw a lot of them that were about different bulbs and wattage and energy efficiency and worried that this was too much like those.

So if I redid my proposal and looked at shields, which light bulb would i use? This seems basic too. A light bulb and a shield. But I thought I could measure lux from above the light with and without the shield and measure lux from a distance with and without the shield and at the base of the light source. I could also create a scale to measure sky glow and glare and spill light/light trespass. This seems more interesting to me but still basic.

Can anyone suggest what I could do to make this more interesting and on a middle school level? Do these ideas sound too elementary school?

Thank you for any help.

As you explore your topic, there are few things to keep in mind.

1) The manufacturers do rate their products on the packaging in lumens. For all practical purposes, any two light bulbs that have the same lumen rating will appear to be same brightness.

2) Light doesn't know what kind of bulb released it. If you make measurements with a 900 lumen 60W incandescent from increasing distances you'll see the same brightness as you'll see from a 8.5W (60W equivalent) 900 lumen LED lamp in that same fixture.

3) Inexpensive meters sold to measure lux can be incredibly color sensitive. CFL and LED bulbs do not put out as full a spectrum as incandescents, so if you use the same 900 lumen bulbs referenced above, a lux meter might say the incandescent is brighter even though it's not.

4) Measuring low level of light accurately may require equipment that's rather expensive. You can make your own equivalent low light meters if it's too expensive to buy one or you can't find one to borrow.

I think you're right that all sorts of projects have been done to measure light efficiency. Since that is mostly about measuring power and light output, and the manufacturers put this information on the package, that alone might be too simple. An experiment related to shielding the light would be something different. If you decide to try that, you'll want to use the same fixture, the same bulb, and make your measurements the same way with the same meter. You'll just be changing the shade or the lamp design to see what effect it has on light leaking outside.

My question would be about how much effect this light spill has when you're far away from turtle habitats. I live about an hour from the ocean - does light coming out of my windows have any effect on turtles? Part of what you may need to answer is how close a house has to be to a habitat to have any effect.

Howard

Typically for science fair projects, it is easier to have only one independent variable, which means you should choose to do only the experiment with the shield, the experiment with the distance of the light, or something else you thought up.

For the shield experiment, you could try testing different types of materials and measure how much light is able to pass through them. For distance, you could do something along the lines of what Howard suggested and measure how far a light source needs to be to minimally disturb turtle habitat.

Also, keep in mind that simplicity is not always a bad thing. Doing simple experiments such as these will help you develop further questions and give you a better idea of what you might enjoy researching.

-Karen