Microwave ovens work by irradiating food with microwave radiation, which is absorbed and converted into heat.
Assuming that radiation with ?=15.0 cm is used, that all the energy is converted to heat, and that 4.184 J is needed to raise the temperature of 1.00 g of water by 1.00 ^0C , how many photons are necessary to raise the temperature of a 350 mL cup of water from 25 ^0C to 95 ^0C?