Question

a. What is the photon energy corresponding to each of these wavelengths?

b.How many total photons does each of these exposures correspond to?

Answer 1

he formula is E = hv
where h = Plancks constant = 6.626*10^-34 J s and v = frequency
For 254 nm, frequency = velocity/wavelength (velocity = c = 3*10^8 m/s)
= 3*10^8/(254*10^-9)
= 0.0118*10^17 s^-1
E = 6.626*10^-34*0.0118*10^17 J
E = 0.0782*10^-17 J
E = 7.82*10^-19 J Answer
and for 3.7*10^-3 J/cm^2 requires 3.7*10^-3/7.82*10^-19 photons/cm^2
= 0.473*10^16 photons/cm^2

for 300 nm wavelength, frequency = 3*10^8/300*10^-9 = 0.01*10^17s^-1
E = 6.626*10^-34*0.01*10^17 J
= 6.63*10^-19 J Answer
and for 13*10^-3 J/cm^3 requires 13*10^-3/6.63*10^-19 photons/cm^2
= 1.961*10^16 photons/cm^2