Question

An experiment is designed to test what color of light will activate a photoelectric cell the best. The photocell is set in a circuit that "clicks" in response to the current. The faster the current, the more clicks per minute. In this experiment, the number of clicks in one minute is recorded for each color of light shining on the photocell. To change the color of light, a different color of cellophane is placed over the same flashlight and the flashlight is then located a specific distance from the photocell.
Which of the following was not kept constant?
1.The color of the light after it has passed through the cellophane
2.The source of the original light
3.The distance of the light from the photocell
4.The test for photocell activation

Answer 1

In the given experiment, the effect of different colors of light on photoelectric cell is determined. The photocell is placed in a circuit that clicks when current passes through it. For each color of light falling on the photocell the number of clicks is measured which gives an idea of the amount of current passing through the cell. Here the independent variable is the color of light. as to change the color of light coming from a common source, different color of cellophane is placed on the same flashlight. The dependent variable is the number of clicks per minute or the current passing through the cell.

Therefore the correct answer will be,

1.The color of the light after it has passed through the cellophane