The resolution limit of electron microscope is

2 V
1 A.V
1.5 A.V
1.2 A.V

The correct answer is: 1.2 A.V.

The resolution limit of an electron microscope is the smallest distance between two objects that can be distinguished as separate objects. It is determined by the wavelength of the electron beam and the numerical aperture of the objective lens. The wavelength of the electron beam is inversely proportional to the accelerating voltage, so higher accelerating voltages result in shorter wavelengths and better resolution. The numerical aperture of the objective lens is a measure of its ability to collect light, and it is also inversely proportional to the wavelength of the light. Therefore, higher numerical apertures result in better resolution.

The resolution limit of an electron microscope is typically about 0.1 nanometers, which is about 100 times better than the resolution of a light microscope. This allows electron microscopes to image objects that are too small to be seen with a light microscope, such as individual atoms and molecules.

Option A: 2 V is not a valid answer. The resolution limit of an electron microscope is not measured in volts.

Option B: 1 A.V is not a valid answer. The resolution limit of an electron microscope is not measured in amperes.

Option C: 1.5 A.V is not a valid answer. The resolution limit of an electron microscope is not measured in angstroms.

Option D: 1.2 A.V is the correct answer. The resolution limit of an electron microscope is typically about 0.1 nanometers, which is about 100 times better than the resolution of a light microscope.