posted by tommy on .
Suppose that the microwave radiation has a wavelength of 12.4 cm. How many photons are required to heat 255 mL of coffee from 25.0 C to 62.0 C? Assume that the coffee has the same density, 0.997 g/mL, and specific heat capacity, 4.184 J/(g/ K), as water over this temperature range.
How much heat is needed to heat the coffee?
q = mass water x specific heat water x (Tfinal-Tintial)
How much energy in 1 photon?
E = hc/wavelength.
Now set up a proportion.
(1 photon/E) = (#photons/q)
solve for # photons.