Question

It is difficult to observe 1-nanometer, 1 millimeter, and 100 meter radiation with ground-based telescopes. What are the reasons for each?

Answer 1

1 nanometer is in x-ray range, so it will be absorbed by most materials lenses would be made of. 1 millimeter is Terahertz/Microwave, so it too will be easily absorbed through phonon energies. 100 meter radiation wouldn't work because your telescope would need to be on the same order of magnitude which is too large.