question_answer 1)

At which of the following frequency/ frequencies the communication will not be reliable for a receiver situated beyond horizon : (a) 10 kHz (b) 10 MHz (c) 1 GHz (d) 1000 GHz  

Answer:

(b) is correct. Here (c) and (d) frequencies have high penetration power so the earth will digest them. Radiation of 10 kHz will suffer from the problem of size of antenna.