[Airthumbs (OP)]

I put my mobile phone into the microwave carefully ensuring that it would not activate when I closed the door.  I watched the signal strength on the phone when I closed the door.  The signal bar only dropped half way each time I closed the door.  As mobile phones work by transmitting and receiving microwaves does that mean when I use my oven microwaves also escape?

[JP]

Cell phones operate over a range of wavelengths, and only some are near those used by microwaves.

You can see a previous discussion with more details here:
http://www.thenakedscientists.com/forum/index.php?topic=41755.0

[confusious says]

The reduced signal you saw was due to the lead (as in metal lead) micromesh casing, which protects you from any radio waves escaping from your oven whilst running, and as this stops radio waves getting out, it also reduces or stops radio waves from your mobile phone transmitter getting to your phone. On the safety aspect, I think all new microwaves are extremely safe, but you can buy a leakage tester, and most leaks if found eminate from around the door seal.

[Bored chemist]

The soft dense metal named lead isn't used in microwave ovens as shielding.