Why does aluminum foil spark in microwave?
Show answer & explanation
Answer: Metal reflects microwaves violently
Foil absorbs too much energy — Wrong. Foil doesn't absorb microwaves well—it reflects them. The problem is this reflection causes electrical buildup and arcing.
Metal reflects microwaves violently ✓ — Correct! Microwaves are electromagnetic waves. Metal reflects them instead of absorbing them like food does. This creates electrical currents in the foil. Sharp edges concentrate these currents, causing sparks (electrical discharge through air). It can damage your microwave!
Foil contains reactive chemicals — Wrong. Aluminum foil is chemically stable. The sparks are purely a physics phenomenon—electromagnetic induction and electrical discharge, not chemistry.