gracegrape13
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Joined: Sun Apr 11, 2021 4:56 am
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May I please have help for my SRP?

Postby gracegrape13 » Sun Apr 11, 2021 5:18 am

I have a school SRP and my question is how the wavelength of light affects the growth (height) of plants. I'm using cellophane as a light filter and watercress as my plant as it will be easier for me to measure height.

However, my school wants us to have both our independent and dependant variables be quantitative. However, I'm uncertain whether the wavelength would be considered quantitative as I'm only using 6 wavelengths (for the 6 colours) and a white light one (without cellophane). As I'm only using 6 specific wavelengths, this means it isn't continuous and I wasn't sure whether it would still be considered as quantitative because it seems more like discrete. Due to this, I also don't know what graph to use either. I was thinking of using scatter graph, but I'm picking 6 specific wavelengths so I wasn't sure if it's correct.


I'm also using white light as a control which is no cellophane. However, white light is a combination of wavelengths. We have to graph our results up, and I'm not sure how to graph up white light since it's multiple wavelengths. I was originally going to use a column graph so I could just say that it is white light, but my school wants it to be quantitative for the independent variable so I have to include the wavelength and I'm not sure how to do it.

I'm so sorry if this is confusing. I would be happy to provide further clarification if I didn't make sense for something. I just really need help.

Any help would be appreciated!

Thanks! :)

MadelineB
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Joined: Fri Jun 20, 2014 4:42 pm
Occupation: Biostatistician/Data Scientist

Re: May I please have help for my SRP?

Postby MadelineB » Sun Apr 11, 2021 3:45 pm

Hello GraceGrape13,

First, I am not a physicist, I'm a biostatistician and data scientist, so I'm going to defer your question about your white light control. I do think that you can make a graph with height on the vertical axis and wavelength on the horizontal axis. In order to show wavelength as a continuous variable, I suggest that you scale the horizontal axis so the distance between each of your 6 wavelenghs is proportional to the wavelength.

It would help me to be more specific if you tell us the specific wavelengths that you tested. Also, how many plants did you test for each of the six wavelenghts? If you tested 3 or more, then I would suggest that you could plot the median height for each of the plants tested at each wavelength. You could also put a dot (or any symbol) for each plant on the plot at their individual height for each wavelength.

Now, how to deal with the white light? One way would be to plot a horizontal line across your graph, at the height of the median for the plants tested in white light (without the cellophane). That would let you (and the judges) compare the results by wavelength versus the results for white light, And drawing the line across the spectrum of light that you tested gets around the issue that white light includes all the wavelengths.

Let me know if this helps and if you have any more questions. Best of luck with your project at your science fair.

Madeline


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