Question

Suppose that the microwave radiation has a wavelength of 10.8cm . How many photons are required to heat 295ml of coffee from 25.0 C to 62.0 C? Assume that the coffee has the same density, 0.997g/ml , and specific heat capacity, 4.184J/(gk) , as water over this temperature range

Answer 1

First, use the density to convert 295 mL to mass H2O. Then calculate the heat required, call it q, to heat that amount of water from 25 to 62.
q = mass H2O x specific heat H2O x (Tfinal-Tinitial).

Now calculate the amount of energy given off by one photon at this wavelength.
E = hc/wavelength. Wavelength must be in meters. h is Planck's constant. c is speed of light in m/s.

The # photons = q(from above)/E(from above)

Answer 2

73