Waves from a radio station have a wavelength of 220 m. they travel by two paths to a home receiver 20.0 km from the transmitter. one path is a direct path, and the second is by reflection from a mountain directly behind the home receiver. what is the minimum distance from the mountain to the receiver that produces destructive interference at the receiver

Given:

wavelength, = 220 m

distance from reciever = 20 km

Solution:

To calculate the path difference in case of the destructive interference:

path difference,           (1)

where m = 0, 1, 2, 3.....

here, m = 0

Therefore, eqn (1) is reduced to:

Now, the minimum distance from mountain to reciever to generate destructive interference at the reciever:

= 55 m

most voltage drop calculators want the distance between the source and destination. then internally, they double it so both the source and return wires are calculated. but you need to know which distance the calculator uses so you're not half of what you should be or double what you should be.

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in your related post, you didn't say what type of load this is. if it is a light or heater, voltage drop won't be a big issue. if this is a motor, the current needs are huge at startup and the voltage drop can pose a problem. if this is a motor, knowing if the motor is under much load during startup will answer the voltage drop effect (a saw is easier to start than a compressor).

photocells convert light energy to electricity