How do radio waves be used to determine the position of icebergs at sea?

Pretend there is a patient and the doctors need to see deep into his body, in a safe way. To start off, they use the MRI, which uses the radio waves to construct a computer image (of the tissue, they are looking at). The MRI device sends a short bursts of radio waves into the paitients body. The radio waves energize atoms (energize the patients particles inside his body)and make them line up. When the radio pulses are turned off the atoms return to there original position and the radio waves return to the machine (when the radio waves come back to the machine or when they return, the machine now has the picture of the tissue).

It is kind of like a delivery man or getting your picture taken. For example, the delivery man... at first it is like a shock you get mail, then when it is done the delivery man leaves. He goes and deliveries it to someone else. So, then that person just recieved whatever you sent. Just like the machine, the machine just got whatever the radio waves gave it... the picture of the tissue.