Question

Microwaves can cause tissue damage. For a microwave, emitting energy, wavelength = 12cm, how many photons must be absorbed to raise the temperature of a human eyeball 3 C? Mass of the eye =11g, specific heat of the eyeball is 4.0 J/g K.

Answer 1

wavelength = 12 cm = 0.12 m
Energy of 1 photon = h*c/wavelength
                                  = (6.626*10^-34 * 3*10^8) / (0.12)
                                  = 1.66*10^-24 J

To raise Temperature by 3oC or 3K, heat required,
Q = m*C*delta T
    = 11*4*3
     =132 J

Number of photon = total energy / energy of 1 photon
                                 = 132/(1.66*10^-24)
                                 =8*10^25
Answer: 8*10^25 photon