Final answer:
The difficulty in seeing interference fringes for light reflected from thick glass compared to a thin film is due to multiple reflections that complicate the interference pattern. Monochromatic light would make it easier to see interference fringes in both thick glass and thin film.
Step-by-step explanation:
The difficulty in seeing interference fringes for light reflected from a thick piece of glass compared to a thin film can be attributed to multiple reflections that complicate the interference pattern in thick glass. As the light reflects multiple times within the thick glass, the interference pattern becomes more complex, making it harder to observe distinct fringes. Additionally, the thicker glass also introduces more dispersion due to its higher index of refraction, which further complicates the interference pattern. Therefore, option b - Multiple reflections complicate the interference pattern in thick glass - is the most accurate explanation for the phenomenon.
If monochromatic light, which consists of a single wavelength, is used instead of white light, it would make it easier to see interference fringes in both thick glass and thin film. Since the interference pattern depends on the ratio of the light's wavelength to the size of the object involved, using monochromatic light would eliminate the variations in color associated with different wavelengths and provide a clearer interference pattern.