Light Colours and PhotosynthesisWhich colour of light is the one that creates an optimum level of photosynthesis?

Group Members:Jimena Vasquez

Ana Cristina FerreiroNicolás Vidrí

Rigoberto Soto

Group 1

BACKGROUND INFORMATION

Carbon Dioxide + Water ( +light) Glucose + Oxygen

• Pond Weed– Is entirely green = chlorophyll

• Chlorophyll– Traps light to use this energy to

photosynthesize

Violet LightThe visible violet light has a wavelength of about 400 nm. Within the visible wavelength spectrum, violet and blue wavelengths are scattered more efficiently than other wavelengths.

Blue LightThe visible blue light has a wavelength of about 475 nm. Because the blue wavelengths are shorter in the visible spectrum, they are scattered more efficiently by the molecules in the atmosphere.

Green LightThe visible green light has a wavelength of about 510 nm. Pond Weed, appears green because all of the colors in the visible part of the spectrum are absorbed into the leaves of the weed except green. Green is reflected, therefore pond weed appears green.Yellow Light

The visible yellow light has a wavelength of about 570 nm.

Orange LightThe visible orange light has a wavelength of about 590 nm.

Red LightThe visible red light has a wavelength of about 650 nm.

AIM

• To find out what colour produces the highest or optimum level of photosynthesis in pond weed.

• Colours:– Red– Orange– Yellow– Green– Blue– Violet

HYPOTHESIS

• Green will produce the least oxygen.• Violet will produce the most oxygen.• Chlorophyll causes green to be reflected,

violet will be more properly absorbed.

WHY?

• This will change because chlorophyll, which is green, traps light in order to photosynthesize, so some colours will be reflected more than others.

VARIABLES

• Independent– the color of the light 

• Dependent– Amount of oxygen produced by plant 

• Controlled– Weed from the same pond, same type,

same area – Light intensity – Amount of time light shines: 10 minutes– Mass of pond weed: 35 grams.

1. Prepare a box.– Hole on top for the bong– Light bulb inside– One end which can be easily opened and

closed2. Prepare separate frames/screens of see-

through color paper.– yellow, orange, blue, purple, green and red.

METHOD

3. Prepare 6 different litter bottles– 10 ml with sodium hydrogen carbonate solution– 35 grams of same pond weed (cut both ends of

the pond weed so the reaction is faster)

3. Setup the box.– Bulb at the back and ready to be plugged in– First screen of colored paper placed in front of the

bulb– bottle with the pond weed at the other end– top of bottle coming out of the box in the hole– The bottle should be closed with a bong with

connects it to a gas syringe which is being hold up by a clamp stand.

DIAGRAMDiagram showing our set up inside the box, using the blue filter.

5. Close the box in a way that no light goes in or out.

6. Turn on the light bulb, start the stopwatch and wait for 10 minutes, record the amount of oxygen produced by reading off the syringe.

7. Repeat steps 4, 5 and 6 with the other five colors. VIDEO

RESULTSColor of

lightWavelength

(nm)Amount of oxygen

produced (ml)

Red 650 15Orange 590 19Yellow 570 5Green 510 3Blue 475 9

Violet 400 10

Violet Blue Green Yellow Orange Red0

2

4

6

8

10

12

14

16

18

20

Rate of Photosynthesis

Light Colour

Amou

nt o

f O

xyge

n (m

l)

• The red filter lets less light pass through compared to the orange filter, therefore our result for photosynthesis in red light is not as effective as in orange light.

• The same applies to the purple and blue filters. Purple should have the highest result, but because the paper only allowed little light to pass through, the result was that the rate was lower. Theoretically, purple should be the most effective because it has the largest wavelength.

• They both let very little light through, and even though they are effective; they are not as effective as they should be.

• This explain the anomalies in our results compared to the predicted results.

CONCLUSION

• Lack of reliability (few trials).• Constant pondweed.• It should be run at least thrice per screen

and averaged out.• Different light sources: Natural or different

types of bulbs.• Different intensities• Use different plants and test their level of

photosynthesis.

EVALUATION