A photon of wavelength 300 nm is absorbed by a gas and then remitted as two photons. One photon is red with wavelength of 760 nm. The wave number of the second photon will be

E=hcλ         ...iE1 =hcλ1        ....iiE2 =hcλ2        ....iiiE=E1 + E2 hCλ=hc1λ1+1λ21λ=1λ1+1λ21300 × 10−9  = 1760 × 10−9 + 1λ21λ2=1300 − 1760 × 10−9=0.00333−0.00131 × 109 =2.02 × 106 m−1