sWriting conclusions in general:

  1. Go back and find out “What is the Purpose?”
  2. Address this in your first sentence!
  3. Incorporate the science concepts related to the experiment where appropriate.
  4. Use evidence to support what is being explored in the experiment. [Data statements]
  5. Make a concluding statement that answers/addresses the purpose.
  6. Extend what was learned from the experiment to more general things that use the scientific concepts.

Conclusion writing for Photosynthesis Part 2

Suggested starting sentence:

In part 2 of the photosynthesis experiment, we have combined the data from all periods. We are comparing the averaged photosynthesis rate from each of 5 lamp sources and the sun. For Photosynthesis to occur, [explain what is needed and what the products are for photosynthesis. What and how did we provide the leaf disks with one of these sources? Again what is the evidence that photosynthesis happened?

  • Lamp 1 and 3 used the same type of bulb (light source) and had different rate averages
  • Lamp #1 had a rate of _____
  • Lamp #3 had a rate of ____
  • Lamp 3 was closer to window, so it could of got more sun light and affected the results
  • Lamp 2 and 3 had very similar rate averages ___ and ___)
  • Lamp 4 showed no signs of photosynthesis (zero disks rose), so UV light does nothave a wavelength of light to allow for photosynthesis to occur
  • Lamp 5 (the one with the long bulb) had a rate average of ___ (rd/min). Therefore this bulb must have a wave length that photosynthesis needs (red wave length)

Use the information from the graphs.

Include what is the approximate range of wavelength that is best for chlorophyll a? What can you say about the lamp sources wavelength of light?

  • Sun had the highest rate at ______RD/min
  • Next highest was ______with a rate of _____
  • ETC……
  • Sun data had variables that changed results like
  • cloud coverage
  • position of sun
  • location of cup
  • time of day
  • bad solution or not fully filled (CO2 in syringe)
  • The more data you have the better/more precise your average will be

Extend by relating to all plants and light sources Houseplants and outside plants.

The following is for those that want to know more.

Photosynthesis is the ability of plants to absorb the energy of light, and convert it into energy for the plant. To do this, plants have pigment molecules which absorb the energy of light very well. The pigment responsible for most light-harvesting by plants is chlorophyll, a green pigment. The green color indicates that it is absorbing all the non-green light-- the blues (~425-450 nm), the reds and yellows (600-700 nm). Red and yellow light is longer wavelength, lower energy light, while the blue light is higher energy. In between the two is green light (~500-550 nm). It seems strange that plants would harvest the lower energy red light instead of the higher energy green light, unless you consider that, like all life, plants first evolved in the ocean. Sea water quickly absorbs the high-energy blue and green light, so that only the lower energy, longer wavelength red light can penetrate into the ocean. Since early plants and still most plant-life today, lived in the ocean, optimizing their pigments to absorb the reds and yellows that were present in ocean water was most effective. While the ability to capture the highest energy blue light was retained, the inability to harvest green light appears to be a consequence of the need to be able to absorb the lower energy of red light.

Plants also use multiple variants of chlorophyll, as well as accessory pigments such as carotenoids (which give carrots their orange color) to tune themselves to absorbing different wavelengths of light. That makes it impossible to assign a single wavelength of best absorption for all plants. All plants, however, has chlorophyll a, which absorbs most strongly at ~450 nm, or a bright blue color. This wavelength is strong in natural sunlight, and somewhat present in incandescent lights, but is very weak in traditional fluorescent lights. Special plant lights increase the amount of light of this wavelength that they produce. But a 400-500 nm wavelength bulb wouldn't be enough, since many plants take cues for germination, flowering, and growth from the presence of red light as well. Good plant lights produce red light as well, giving plants all the wavelengths of light they need for proper growth.

Our eyes are sensitive to light which lies in a very small region of the electromagnetic spectrum labeled "visible light". This "visible light" corresponds to a wavelength range of 400 - 700 nanometers (nm) and a color range of violet through red. The human eye is not capable of "seeing" radiation with wavelengths outside the visible spectrum. The visible colors from shortest to longest wavelength are: violet, blue, green, yellow, orange, and red. Ultraviolet radiation has a shorter wavelength than the visible violet light. Infrared radiation has a longer wavelength than visible red light. The white light is a mixture of the colors of the visible spectrum. Black is a total absence of light.
Earth's most important energy source is the Sun. Sunlight consists of the entire electromagnetic spectrum.
Learn more:
  • Violet light.
  • Indigo light.
  • Blue light.
  • Green light.
  • Yellow light.
  • Orange light.
  • Red light.
  • Wavelengths that humans cannot see.
  • Determining wavelengths.
  • SkyServer page about color.
  • Make a Splash with Color.
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(Wavelength image from Universe by Freedman and Kaufmann.)
Violet Light
The 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. The sky looks blue, not violet, because our eyes are more sensitive to blue light (the sun also emits more energy as blue light than as violet).
Indigo Light
The visible indigo light has a wavelength of about 445 nm.
Blue Light
The 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. This causes the sky to appear blue during the main part of the day, when blue light is scattered into your eye no matter which direction you look. /
Green Light
The visible green light has a wavelength of about 510 nm. Grass, for example, appears green because all of the colors in the visible part of the spectrum are absorbed into the leaves of the grass except green. Green is reflected, therefore grass appears green. /
Yellow Light
The visible yellow light has a wavelength of about 570 nm. /
Orange Light
The visible orange light has a wavelength of about 590 nm. Low-pressure sodium lamps, like those used in some parking lots, emit a orange-ish (wavelength 589 nm) light.
Red Light
The visible red light has a wavelength of about 650 nm. At sunrise and sunset, the light you see has traveled a longer distance through the atmosphere. A large amount of blue and violet light has been removed as a result of scattering and the longwave colors, such as red and orange, are more readily seen. /

Colors We Can't See

There are many wavelengths in the electromagnetic spectrum the human eye cannot detect.

Energy with wavelengths too short for humans to see

Energy with wavelengths too short to see is "more violet than violet". Light with such short wavelengths is called "Ultraviolet" light.
The term "ultra-" means higher than.

How do we know this light exists? One way is that this kind of light causes sunburns. Our skin is sensitive to this kind of light. If we stay out in this light without sunblock protection, our skin absorbs this energy. After the energy is absorbed, it can make our skin change color ("tan") or it can break down the cells and cause other damage.

Energy with wavelengths too long for humans to see

Energy whose wavelength is too long to see is "redder than red". Light with such long wavelengths is called "Infrared" light. The term "Infra-" means "lower than".

How do we know this kind of light exists? One way is that we can feel energy with these wavelengths such as when we sit in front of a campfire or when we get close to a stove burner. Scientists like Samuel Pierpont Langley passed light through a prism and discovered that the infrared light the scientists could not see beyond red could make other things hot.

Very long wavelengths of infrared light radiate heat to outer space. This radiation is important to the Earth's energy budget. If this energy did not escape to space, the solar energy that the Earth absorbs would continue to heat the Earth.