A dental xray typically affects 205 g of tissue and delivers

A dental x-ray typically affects 205 g of tissue and delivers about 3.95 muJ of energy using x-rays that have wavelengths of 0.0225 nm. What is the energy (in electron volts) of a single photon of these x-rays? How many photons are absorbed during the dental x-ray?

Solution

A.

E=hc/lambda

E = (6.62*10^-34*3*10^8)/(0.0225*10^-9)

E = 8.82*10^-15 J = 8.82*10^-15/(1.6*10^-19) eV

E = 55125 eV = 55.125 keV

B.

The energy, E = 55.125 keV = 8.82*10^-15 J

Number of photons, n = total energy/ energy of photon
n = 3.95*10^-6/(8.82*10^-15)
n = 4.47*10^8 photons