Final answer:
Statement-1 about the fringe pattern shifting when a thin film is introduced in YDSE is true, while Statement-2 about unequal slit widths causing the minima to not be completely dark in YDSE is false. So, the appropriate answer choice would be that Statement-1 is true, Statement-2 is false.
Step-by-step explanation:
Let's evaluate the statements provided:
Statement-1 Evaluation
In Young's Double Slit Experiment (YDSE), if a thin film is introduced in front of the upper slit, then the fringe pattern shifts. This statement is true. The introduction of a thin film adds an additional optical path length for the waves passing through that slit. Because the light now travels a longer effective distance, this causes a phase change, shifting the interference pattern in a direction that corresponds to the extra path – typically downward if the film is in front of the upper slit.
Statement-2 Evaluation
Regarding whether unequal slit widths would cause the minima to be completely dark, this statement is false. The dark fringes (minima) in the interference pattern are a result of destructive interference, which occurs when two waves are out of phase. Unequal slit widths might affect the intensity of the fringes due to differing amounts of light emanating from each slit, but it does not prevent the occurrence of completely dark minima if the path difference corresponds to an odd multiple of half wavelengths.
Therefore, the correct option is: C. Statement-1 is true, Statement-2 is false.