Which form of radiation should give the highest resolution image?

Answer 1

The shorter the wavelength, the higher the resolution. However, shorter wavelength radiation also is much more energetic, meaning that it's harder to focus. So, the answer to your question is gamma rays (especially far gamma rays), but realistically, they're impossible to focus.

Answer 2

In general, the higher the frequency, the shorter the wavelength and the better the resolution. Very long wavelengths, like radar, can only show you that there is something out there, but not it's shape to any fine detail. Visible light shows detail down to the level of skin pores, fingerprints, etc. X rays are even finer, but they tend to penetrate and show ghost images of stuff that they pass through. Electron beams - as in electron microscopes, are probably the highest resolution available - but they still cannot provide a perfect image, which is always just beyond our grasp.

Answer 3

Electromagnetic radiation contains all of the visible and invisible rays we humans know how to image.
Very specific wavelengths offer truly spectacular views (like a Hydrogen alpha filter when looking at the Sun).
It all depends upon what the observer is looking for... What he or she is trying to learn. Visible wavelengths are what we are all used to... It's the range of electromagnetic radiation that our eyes operate in.
Different images can be obtained by observing in different wavelengths (radio, infrared, ultrviolet, X-ray and Gamma- ray).
These images can be combined to paint the clearest possible picture of a specific target.