Final answer:
Whether ignoring the walls' effect on light paths in an experiment is fair depends on the experimental setup and the phenomena being studied. Assumptions should be carefully considered as they can affect the outcome of the experiment.
Step-by-step explanation:
In physics experiments involving light, it is important to consider the effect that the surroundings may have on the path of light. When you conduct an experiment and choose to ignore the effect that the walls of your box have on the path of light, whether this is a fair assumption or not depends on the circumstances of the experiment. For example, in the double-slit experiment or when studying the laws of reflection, you can often ignore the diffraction effect if the slits are very narrow or the surface is a perfect mirror. However, if the slits are wider or the surfaces uneven, you cannot neglect the interplay between light and the materials it encounters.
Einstein's theories and Maxwell's equations inform us that light travels in straight lines but can exhibit complex behaviors like bending or spreading under certain conditions. When considering an experiment related to the propagation of light, it's vital to evaluate the assumptions you're making about the light's interaction with the environment. If the walls of your box have properties that could cause reflection, refraction or diffraction, and these effects are significant to the outcomes you're measuring, then neglecting the box's effect on light may introduce errors into your results.