In reading the instruction manual that came with your garage-door opener, you see that the transmitter unit in your car produces a 250 mW signal and that the receiver
unit is supposed to respond to a radio wave of the correct frequency if the electric
field amplitude exceeds 0.10 V/m. You wonder if this is really true. To find out, you
put fresh batteries in the transmitter and start walking away from your garage while
opening and closing the door. Your garage door finally fails to respond when you're
42 m away. What is the actual power of your transmitter unit?
Note: Your answer is assumed to be reduced to the highest power possible.
Your