[schemathings]

Was curious .. google turned up this http://rabi.phys.virginia.edu/1060/1999/final_answers.html

A satellite dish is actually a mirror telescope for microwaves, with its receiving antenna located at the real image of the distant satellite. But unlike the smooth, shiny mirror of a light telescope, a typical satellite dish is made of dull metallic mesh. Microwaves reflect almost perfectly from this mesh because

Answer: (A) its holes are much smaller than the wavelength of the microwaves.