Cell phones/radios in flight...

[lifesaver]

So why cant we use cell phones and radios in flight? I know it has something to do with the frequency of radio waves. Why does a radio emit waves, but not a Discman? Will my plane fall out of the sky if Joe Traveler forgets his phone is on? How about if my walkman in my bag gets jostled and accidentally gets switched on? How many cell phones and radios are too many? I know it has something to do with the transponder (the thing that tells the tower where the plane is) and radio wave frequencies.

Can maybe an engineer on here (calling AlphaSigOU) help with an explanation - and incluse soem scientific soundin stuff? I am flying on Friday and I’ll be wondering the whole flight. Thanks.