Question

The laser pointer emits light because electrons in the material are excited (by a battery) from their ground state to an upper excited state. When the electrons return to the ground state, they lose the excess energy in the form of 545-nm photons. What is the energy gap between the ground state and excited state in the laser material?

Answer 1

Answer: 1.08 x 10^-19 J/electron

Explanation:

By conservation of energy, the energy gap between excited state and ground state must equal the photon energy. The energy of a photon with wavelength lambda is h*c/lambda, where h is Planck's constant and c is the speed of light.

(6.626*10^-34)(3.00*10^8)/(5.45*10^-7)= 1.08*10^-19

Answer 2

Answer:

E = 2.15ev or 3.45*10⁻¹⁹J

Explanation:

E = hc / λ

E = energy of photon

h = plancks constant = 6.626*10⁻34 m²kg / s

c = speed of light = 3.0*10⁸ m/s

λ = wavelength of the photon = 545nm = 545*10⁻⁹m

E = hc / λ

E = (6.626*10⁻³⁴ * 3.0*10⁸) / (545*10⁻⁹)

E = 3.449 *10⁻¹⁹J

E = 3.45*10⁻¹⁹

1eV = 1.602*10⁻¹⁹J

xeV = 3.45*10⁻¹⁹

E = 2.15eV