You load the web page on your phone, put it in to the microwave and close the door. The microwave should be a Faraday cage preventing microwave radiation getting through. Now the phone/web page cannot contact the internet. The chart stops updating.

Unless there's a leak, then the chart continues updating while the phone is in the microwave.

Then open the door and look if it could/couldn't keep pinging the server while the door was closed.