That would take an awful long lead at 2450 mHz. The speed of light divided by that is 1.2 meters. Where can you get a 30 centimeter mechanical pencil lead?
Oops, 3e8 not 3e9. 3 cm would do it. Somewhat over an inch.
" The speed of light divided by that is 1.2 meters."
From Wikipedi:
"A microwave oven works by passing microwave radiation, usually at a frequency of 2450 MHz (a wavelength of 12.24 cm), through the food. Water, fat, and sugar molecules in the food absorb energy from the microwave beam in a process called dielectric heating. Many molecules (such as those of water) are electric dipoles, meaning that they have a positive charge at one end and a negative charge at the other, and therefore rotate as they try to align themselves with the alternating electric field induced by the microwave beam. This molecular movement creates heat as the rotating molecules hit other molecules and put them into motion. Microwave heating is most efficient on liquid water, and much less so on fats and sugars (which have less molecular dipole moment), and frozen water (where the molecules are not free to rotate). Microwave heating is sometimes incorrectly explained as a rotational resonance of water molecules: such resonance only occurs at much higher frequencies, in the tens of gigahertz. Moreover, large industrial/commercial microwave ovens operating in the 900 MHz range also heat water and food perfectly well."
12.4 cm is 4.8 inches, making a 1/4 wavelength 1.2 inches....