Why are radio observatories located in valleys far away from urban centers?

A. to shield them from electromagnetic interference

B. to avoid sound pollution

C. to avoid disturbing people living in the city

D. to shield them from water vapor

A. to shield them from electromagnetic interference

Explanation:

Radio observatories have to be placed away from urban centers to avoid electromagnetic interference from radio, television and other man-made devices. They have to be shielded since they detect the radio waves from astronomical radio sources. This type of observatory observes the radio frequency portion of the electromagnetic spectrum emitted by astronomical objects. In contrast, the optical telescopes observe the light wave portion of the spectrum coming from astronomical objects.