The figure shown above shows the energy levels for a hydrogen atom. what is the energy of the photon emitted when the electron in a hydrogen atom drops from energy level e5 to energy level e2?

The energy of the photon emitted when the electron in a hydrogen atom drops from energy level E5 to energy level E2 is 2.85eV

Now, the energy of the ground state is -13.6 eV.
the energy of the first state (n = 1) is -3.39 eV.
the energy of the fifth state is -0.54 eV.

Now, When an electron drops from higher to lower state, then energy difference is same as the energy of the photon emitted, is
 = E5 - E2
= -0.54 eV -(-3.39 eV)
= 2.85 eV 

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