For a source S1, Wavelength, λ1=5000Å Number of photons emitted per second, N1=1015 Energy of each photon, E1=‌
hc
λ1
Power of source S1,P1=E1N1=‌N1hc∕λ1 For a source S2, Wavelength, λ22=5100Å Number of photons emitted per second, N2=1.02×1015 Energy of each photon, E2=‌