Question

can some body give me the correct answer for.when observer is near the electron screen the output is not correct but when the observer is not there we can get the correct pattern

Answer 1

Probably because the sub-atomic particles of the observer's body effect those of the electron screen due to force-interaction and hence the output gets altered and is not correct. However, in the absence of an observer, the electrons face not a very significant amount of interference in their configuration.