An excited atom decays to its ground state and emits a photon of green light. if instead the atom decays to an intermediate state, then the light emitted could be

the light emitting must be of greater wavelength

Explanation:

For this exercise we must use the Planck equation

             E = h f

And the speed of light

            c = λ f

            f = c / λ

We replace

            E = h c / λ

The wavelength of the green light is of the order of 500 nm, let's calculate the energy

          E = 6.63 10⁻³⁴  3 10⁸ /λ

          E = 1,989 10⁻²⁵ /λ

          λ = 500 nm = 500 10⁻⁹ m

          E = 1,989 10⁻²⁵ / 500 10⁻⁹

          E = 3,978 10⁻¹⁹ J

That is the energy of the transition for a transition is an intermediate state the energy must be less, this implies that the wavelength must increase. For the explicit case of a state with half of this energy

            = E / 2

              = 3,978 10⁻¹⁹ / 2 = 1,989 10⁻¹⁹

Let's clear and calculate

           λ = h c / E

           λ = 1,989 10⁻²⁵ / 1,989 10⁻¹⁹

           λ = 1 10⁻⁶ m

Let's reduce to nm

          λ = 1000 nm

This wavelength is in the infrared region

the light emitting must be of greater wavelength

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