Microwave and EMP

[thinwater]

In the movie "Snowdon" they put cell phones in the microwave to block the signal. Conventional wisdom is that the microwave will block EMP in the event of lightening.

So how come my phone still rings if it is in the microwave?

Urban legend? A difference in frequencies? A difference in sensitivity?

[adoxograph]

Originally Posted by thinwater

In the movie "Snowdon" they put cell phones in the microwave to block the signal. Conventional wisdom is that the microwave will block EMP in the event of lightening.

So how come my phone still rings if it is in the microwave?

Urban legend? A difference in frequencies? A difference in sensitivity?

Movie BS or artistic license, call it what you want.

A microwave oven in this context is nothing but a Faraday cage. Put something in there and it is save from external electrical fields i.e. caused by lightning. The high voltage (not the EMP) of a lightning strike will fry all your electronic equipment. A Faraday cage causes the electric charges to be distributed in a way that they cancel the field's effect in the cage's interior.

Now some EM radiation, i.e. your phones radio waves, pass through and are not effected by the Faraday cage. It is a common myth is that a Faraday cage provides full blockage or attenuation. A Faraday cage has varied attenuation depending on wave form, frequency or distance from receiver/transmitter, and receiver/transmitter power.

[hafa]

What you did not notice in the movie was that they turned on the microwave after placing the phones inside. No problems with those phones inadvertently broadcasting, or the microwave overheating food in the future...