WandaPanda
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Glowstick Experiment Modification

Postby WandaPanda » Sun Aug 18, 2019 7:09 pm

Hi, I was looking at the glowstick procedure, and I was wondering if there is a way to modify the experiment to find the illumination (how bright something is) rather than the resistance.

Link to Experiment: https://www.sciencebuddies.org/science- ... #procedure

bfinio
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Re: Glowstick Experiment Modification

Postby bfinio » Mon Aug 19, 2019 8:37 am

Hi,

You can get this information from the data sheet for the photoresistor (this assumes you bought the Science Buddies kit - otherwise, you will need to find the data sheet for the photoresistor you bought)

https://www.jameco.com/Jameco/Products/ ... 202420.pdf

There is a graph titled "Typical Resistance vs. Variable Illumination." This allows you to convert ohms to lux, a unit used to measure light.

Note that there are a lot of different units used to measure light (such as the lumen and candela). Technically lux is a measure of "illuminance" which is not the same thing as "illumination." https://en.wikipedia.org/wiki/Lux

Hope that helps,

Ben

WandaPanda
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Joined: Sun Aug 18, 2019 7:02 pm
Occupation: Student

Re: Glowstick Experiment Modification

Postby WandaPanda » Mon Aug 19, 2019 4:27 pm

Thanks!

I just want to clarify one thing. My experiment is based on my dependent variable being light brightness (illuminance), while my independent variable is temperature. Does the graph require any specific circumstances that I need to control in the experiment in order for it to provide me with correct information?

bfinio
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Re: Glowstick Experiment Modification

Postby bfinio » Mon Aug 19, 2019 5:12 pm

Hi WandaPanda,

The section above the graph says "Electrical Characteristics (at 25 deg C)," so it probably means that data was collected at approximately room temperature. Unfortunately, there's nothing on the datasheet about a temperature coefficient, or anything about readings at different temperatures, so that graph is the best you have to go with. What temperature range will you be testing? The datasheet indicates that the maximum temperature range goes from -25 to +75 deg C, so as long as you aren't going outside that range, you probably won't break or destroy the photoresistor, and I'd say you can assume the graph is still reliable.

Don't hesitate to write back if you have more questions.

-Ben

WandaPanda
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Occupation: Student

Re: Glowstick Experiment Modification

Postby WandaPanda » Wed Aug 21, 2019 5:38 pm

How would I read the graph, since I see two slopes? Would the higher slope be maximum illuminance whereas the lower slope be the minimum illuminance?

bfinio
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Re: Glowstick Experiment Modification

Postby bfinio » Fri Aug 23, 2019 6:00 am

Hi - you're correct, the two lines on the graph show a range. You'll also notice that the data table above lists "Min" and "Max" values. So if you just wanted to take a single "average" value, I'd say you can draw a new line exactly halfway between the two existing lines, and use that as your best guess. If you want to give an error range then you should also report the minimum and maximum values.


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