There are several factors that could contribute to the variation in recorded luminance during your experiment, even when using controlled light sources. Here are a few potential factors to consider:
Measurement Error: Variations in the measurement equipment or technique can introduce inaccuracies. Ensure that the instrument used to measure luminance is calibrated properly and that the measurements are taken consistently and accurately.
Sensor Sensitivity: The sensitivity of the light sensor used to measure luminance may vary slightly, even if it is designed to be consistent. Small differences in sensor performance, such as variations in the manufacturing process or aging, can lead to variations in recorded values.
Ambient Light Interference: Even in a dark room, there might be some residual ambient light that could influence the measurements. This could be external light leaking into the room, reflections from nearby surfaces, or the presence of electronic displays or indicator lights that emit light. These sources can contribute to fluctuations in recorded luminance.
Electrical Fluctuations: Power supply fluctuations or electromagnetic interference can affect the output of your controlled light sources, resulting in variations in luminance readings. Check the stability of the power source and ensure that the electrical connections are secure.
Thermal Effects: Light sources generate heat, and temperature variations can affect their performance. Changes in temperature can impact the output of the light sources and, consequently, the recorded luminance. Make sure the room temperature remains stable throughout the experiment.
Human Error: Human factors, such as unintentional movement or slight changes in the experimental setup, can introduce variations in recorded luminance. Ensure that the experimental conditions are consistent and that external factors, like someone inadvertently blocking or partially obstructing the light, are minimized.
It's essential to consider these potential factors and evaluate their impact on your experimental setup. By carefully controlling and mitigating these sources of variation, you can improve the reliability and accuracy of your measurements.