Stuck on this physics problem! As a newly-commissioned officer in the US Navy, y
ID: 1288030 • Letter: S
Question
Stuck on this physics problem!
As a newly-commissioned officer in the US Navy, your team is tasked with updating the communication system used by our submarines. Your first step is describe the problem to your superior officers:
1) How deep could submarines operate?
2) If a communication signal reaches the top of the ocean with an intensity of 100Wm2, what is the signal intensity at the depth of the submarine (remember to use for saltwater not 0)
3) If your broadcast station is in China Lake, CA and your submarine is off the coast of the Kamchatka Peninsula, what broadcast power do you need to get 100Wm2 at the surface of the water above the submarine? Because higher frequency signals are absorbed by water, submarines typically use ELF (Extremely Low Frequency) to receive orders. If the orders are sent using morse code using a frequency of 1Hz:
4) How long would it take to receive a 1 page order (400 words)?
5) How long should an ideal antenna be (recall the length =4)? Is this realistic?
6) If the submarine is traveling at 1km/h, how long would it take to unspool the antenna?
Explanation / Answer
1)
U.S. Navy submarines can submerge deeper than 800 feet. The actual depth is classified, but it is less than the deep-diving U.S. Navy-supported civilian research submarines that explore the bottom of the oceans.
2)
The signal intensity will be 9 times greater at the surface .Therefore the signal intensity in the submarine is 900W/m^2.
3)
It actually depends on the distance between the sending and receiving stations situated. But if the position is mentioned, and use 1Hz morse code for sending the signal, then the power generated should be greater than or equal to 2300W/m^2.
4)
One page order will take 30seconds to be received ...from the sender.
5)
As per the relation of wavelength of send signal and length of the antennae, in this situation it takes an antennae of 15km to be used, which is obviously impractical
6)
Unspooling the antennae will take a time of 12 minutes from the submarine