Correct Answer : SONAR
Explanation : SONAR or SOund Navigation and Ranging is the transmission of information using sound waves. Since seawater is saline, it shorts out the electrical field in the radio waves and hence radio communication cannot be used.
Correct Answer : Option (D) : 1477.8Mhz
Explanation : Wavelength =8 in.= 0.203 mFrequency = 300/0.203 = 1477.8Mhz.
Correct Answer : Option (B) : Satellite communication
Explanation : SHFs or Super High Frequency EM waves are those which lie between the frequency range of 3 to 30GHz range. These microwaves frequencies are widely used in satellite communication and radar.
Correct Answer : Option (B) : Books
Explanation : Infrared radiation is generally associated with heat. Infrared is produced by light bulbs, human bodies, and basically any physical equipment that generates heat.