The propagation speed of microwave in air is about equal to the speed of light (that is, 3× 108 m/s).
When f = 3×101Hz, λ = 3×108m/S3×101Hz =1Hz.
(2) Using high-voltage transmission, according to the formula P=UI, if the power is constant, the voltage will increase and the current will decrease. According to the formula W=I2Rt, it can be seen that the current will be reduced, thus reducing the power loss of the transmission line.
Hydroelectric power generation is to convert the mechanical energy of geomantic omen into electrical energy. The advantages of hydropower are no environmental pollution and comprehensive utilization of natural resources.
So the answer is
(1) hive; 10-3; (2) reducing the power loss on the transmission line; No pollution to the environment, comprehensive utilization of natural resources.