Final answer:
Statement-I is correct as the interference pattern in Young's experiment relies on having two coherent light sources; closing one slit removes the interference. Complete destructive interference across the entire pattern is impossible due to the nature of wave interference.
Step-by-step explanation:
The student's question is related to Young's double-slit experiment and the phenomenon of interference patterns. When performing Young's double-slit experiment, closing one of the slits does indeed cause the interference pattern to disappear. This is because an interference pattern is the result of the superposition of light waves from two coherent light sources, which in the case of Young's experiment, are the two slits acting as these coherent sources. When one slit is closed, only one wavefront is present, and hence there is no other wave to interfere with. Therefore, Statement-I is true: the interference pattern does disappear when one of the slits is closed.
Regarding the second assertion, creating a setup where there is only destructive interference is not possible. This is due to the fact that destructive interference occurs at specific points where the path difference between the two waves is an odd multiple of half the wavelength, causing them to cancel each other out. However, at other points, there will be constructive or partial interference. Thus, complete destructive interference over the entire pattern is not attainable.