Microwave ovens heat food by creating microwave electromagnetic radiation that i
ID: 795145 • Letter: M
Question
Microwave ovens heat food by creating microwave electromagnetic radiation that is absorbed by water molecules in the food. Any material that does not have water in it will not absorb the radiation and will not get hot. Metals reflect the microwaves from their surfaces and disrupt the operation of the oven. Some Australians heat water in microwave ovens to make tea. What is the minimum number of microwave photons with a wavelength of 3.35 mm that will have to be absorbed by a 125.00 gram sample of water to heat it from 25
Explanation / Answer
Total energy required = 125.00 x 315 = 39375 J
Energy of 1 photon = hc/wavelength
= 6.626 x 10^(-34) x 2.998 x 10^8/3.35 x 10^(-3)
= 5.930 x 10^(-23) J
Number of photons = total energy/energy of 1 photon
= 39375/5.930 x 10^(-23)
= 6.64 x 10^26 photons