Another energy fluence question work shown

[johnq2k7]

An x-ray field at a point P contains 7.5 x 10^8 photons/m^2-sec-keV, uniformly distributed from 10 to 100 keV.

a.) What is the photon flux density at P?
b.) What would be the photon fluence in one hour?
c.) What is the corresponding energy fluence in SI units?


work shown:


a.) 7.5 x 10^8 photons/m^2-sec-keV x (100 keV- 10 keV)= 6.75 x 10^10 photons/m^2-sec
-this answer is correct
b.) 6.75 x 10^10 photons/m^2-sec * (3600 sec/1hr)= 2.43 x 10^14 photons/m^2
-this answer is correct

c.) i need help here,

7.5 x 10^8 photons/m^2-sec-keV x (3600 sec/ 1hr) *(100-10 keV)
= 2.43 x 10^14 photons/m^2 how do i convert to J/m^2 here

like basically I have to convert photons to Joules, but how do i do this?
the correct answer is apparently 2.14 J/m^2 but i can't get the answer


please help!

 

[RWS_Rasta]

You have to multiply the 2.43E14 photons/m^2 to the Expectation value of the photon energy, which is (0.100 MeV + 0.010 MeV)/2, then multiply that result to 1.602E-13 J/MeV. The answer is 2.14 J/m^2.