A gas absorbs a photon of 355 nm and emits at two wavelengths. if one of the emissions is at 680 nm, what will be next wavelength emitted?

According to the Law of conservation energy, the absorbed photon must be equal to the combines energy of two emitted photons

ET = E1 + E2 + …–(1)

where E1 and E2 are the Energy of first and second emitted photon

E= hc/λ –(2)

h= Planck’s constant c is the velocity of light

λ = wavelength

From (1) and (2)

hc/λT = hc/λ1 + hc/λ2

-> 1/λt = 1/λ1 + 1/λ2

Substitute the values

1/355 = 1/680 + 1/λ2

1/λ2 = 68-355/355*680

λ2 = 742nm