Passage IV
Photosynthesis is the process by which green plants convert light energy into chemical energy. The process is shown in the generalized reaction below.
To study photosynthesis in the plant Elodea, a scientist conducted three experiments using the apparatus shown in Figure 1 below. In each experiment, the cut end of a 5-inch length of Elodea was inserted into the opening of an inverted graduated cylinder in Beaker A. All tests were conducted using a 60-watt floodlamp in a room at constant temperature. The amount of oxygen (O2) produced in the graduated cylinder, in milliliters (mL), was used as an estimate of the photosynthetic activity. The results from all three experiments are reported in Table 1.
Experiment 1
In this experiment, the effect of light intensity was studied. The distance between the floodlamp and Beaker A was varied. In each test, the amount of O2 produced after 10 minutes was recorded.
Experiment 2
In this experiment, the effect of light duration was studied. The amount of O2 produced in the graduated cylinder after various durations of light exposure was recorded.
Experiment 3
In this experiment, the effect of light color was studied. Filters of different colors were placed between Beaker A and Beaker B. Only wavelengths of light the same color as each filter could pass through the filters.
23. Based on the results of all three experiments, under which of the following sets of experimental conditions would the LEAST amount of O2 be produced?
Your Answer is
Correct Answer is D
Explanation
The farther the light source is, the shorter the time is, the weaker the photosynthesis is, and the less oxygen is produced. Adding a filter can shield part of the light, which is equivalent to weakening the light source and photosynthesis, so choose D