Answer:
minimum number of photon is 4.05 × [tex]10^{7}[/tex]
Explanation:
given data
energy = 50 keV = 50 × [tex]10^{3}[/tex] eV =  50 × [tex]10^{3}[/tex] × 1.602× [tex]10^{-19}[/tex]  J
thickness = 10^-3
contrast = 1%
to find out
number of incident photons
solution
we know here equation that is
E  = n  × h  × ν  .......................1
put here all these value
50 × [tex]10^{3}[/tex] = n × 6.6× [tex]10^{-34}[/tex] × c/ 1× [tex]10^{-3}[/tex]
50 × [tex]10^{3}[/tex] × 1.602× [tex]10^{-19}[/tex]  = n × 6.6× [tex]10^{-34}[/tex] ×( 3 × [tex]10^{8}[/tex] / 1× [tex]10^{-3}[/tex])
solve it and find n
n = 4.05 × [tex]10^{7}[/tex]
so here minimum number of photon is 4.05 × [tex]10^{7}[/tex]