A lossless antenna with directive gain of 8 dBi is fed with a 2 W power. The total radiated power of the antenna will be:
i. 16 W
ii. 8 W
iii. 4 W
iv. 2 W

Question

A lossless antenna with directive gain of 8 dBi is fed with a 2 W power. The total radiated power of the antenna will be:
i. 16 W
ii. 8 W
iii. 4 W
iv. 2 W

anonymous · Answer

It's 2W.  There's no gain in power...just power density.  Directivity describes the peak power density relative to an isotropic source.  An ideal isotropic antenna would uniformly radiate the same power at any equi-distant point.  

     An analogy would be comparing a candle and another candle with a reflector placed on one side.  They both radiate the same power, but the one with the reflector shines a larger proportion of its power in the direction away from the reflector.