A certain microwave oven delivers 750. watts (joule/s) of power to a coffee cup containing 50.0 g of water at 25.0C.

If the wavelength of the microwave in the oven is 9.75cm, how long does it take and how many photons must be absorbed, to make the water boil? The specific heat capacity is 4.18J*C^-1g^-1. Assume that only the water absorbs the energy of the microwave.

Answer:- Solving for the amount of heat needed to boil the water.

Heat gained by water=m×Cp×ΔTHeat gained by water=50.0g×4.18Jg⋅∘C×\(100−25)∘CHeat gained by water=15,675J

15,675 Joules is needed to heat 50.0 grams of water from 25 degrees Celsius to 100 degrees Celsius.  We will now compute the number of photons that must be absorbed to boil the water.

15,675J×1photon2.04×10−24J=7.68×1027photons

7.68×1027

Photons are needed to boil the water.