A helium-neon laser can produce a green laser beam instead of a red one. The fig

Question

A helium-neon laser can produce a green laser beam instead of a red one. The figure below shows the transitions involved to form the red beam and the green beam. After a population inversion is established, neon atoms make a variety of downward transitions in falling from the state labeled E4* down eventually to level E1 (arbitrarily assigned the energy E1 = 0). The atoms emit both red light with a wavelength of 632.8 nm in a transition E4* − E3 and green light with a wavelength of 543 nm in a competing transition E4* − E2.

Explanation / Answer

E = hf

light speed is c

L*f = c

solve for f

f = c/L

substitute into E = hf

E = hc/L

we now have energy per wavelength

E4 - E3 = delta E43

E4 - E2 = delta E42

deltaE42 = (hc/543)*10^9

deltaE42 = 6.626*10^-34*3*10^8*10^9/543

deltaE42 = 2.28 eV

deltaE43 = (hc/632.8)*10^9

since we know E4 = 20.66 eV

E2 = E4 - deltaE42

E2 = 20.66 - 2.28

E2 = 18.38 eV

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