X-ray telescopes: Question 14 options: are of no interest because astronomical objects do not give off X-rays have to be made fantastically large to resolve details; so far, none is in operation (although one is planned) rely on the fact that X-rays can bounce off mirrored surfaces, like stones skipping on the water, at what is called "grazing incidence" are impossible to build because the X-rays would merely pass through any ordinary mirrors intended to collect the light