Science Questions

Could you make a phone call with a mobile phone in a car, underwater at the bottom of a river? Troy McLuham, Second Life

Chris -   What he’s getting at, is that radio waves do not propagate very well through water.  Part of the reason is a radio wave is an electromagnetic wave and as water contains lots of dissolved salts and ions, you can’t get the signal to go very far.  That’s why submarines, when they're underwater, they can’t communicate very easily.  They have to surface or they can only communicate with limited range and they tend to use sonar because sound travels very, very easily underwater but radio waves are soaked up by the fact that they are a moving electromagnetic wave and this makes the ions in the water go backwards and forwards and so, you lose all your energy in your radio wave very quickly underwater.

Ben -   Right  So, I wonder, should you happen to be trapped in a car underwater at the bottom of a river, how on earth do you get somebody to come and help you?

Chris -   I think you have to get out.  I don’t think that your mobile phone signal is going to spread very far, unfortunately.

July 2009