An electron falling from one energy level to another emits a photon of wavelength 550nm. What is the difference between the two energy levels?
The key equation is that of the energy of a photon.
E = hc/λ
Using λ = 550nm gives E = 3.61x10^-19J (Remember that a nanometer is 1x10^-9 m).
Using the conservation of energy, the energy of this photon must be the energy lost by the electron.
Hence, the energy gap E = 3.61x10^-19J
JL
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