In the visible optical region, tissue scattering dominates absorption. Assume the scattering coefficient of a 5-cm thick tissue is 100 cm-1 and the wavelength of light is 0:5 mm. In order to detect on average a single ballistic photon transmitted through the tissue, what is the energy in Joules that is required for the incident light? Compare the energy of the incident light with the rest energy of the earth using Einstein's mass-energy equivalence equation E = mc2, where the mass of the earth is 6 x1024 kg.