Simpler explanation of what happens:

The aluminum layer in a CD-ROM is very thin. The microwave oven induces large currents in the aluminum. This makes enough heat to vaporize the aluminum. You then see a very small lightning storm as electric arcs go through the vaporized aluminum. Within a few seconds there will be many paths etched through the aluminum, leaving behind little metallic islands. Some of the islands will be shaped so that they make very good microwave antennas. These spots will focus the microwave energy, and get very hot. Now you will see just a few bright spots spewing a lot of smoke.

• http://hamjudo.com/notes/cdrom.html

More detailed explanation:

• http://raptor.physics.wisc.edu/wacky/cd/

Other sites:

• http://www.eskimo.com/~billb/weird/microexp.html
• http://howthingswork.virginia.edu/microwave_ovens.html archive copy at the Wayback Machine

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