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 521-nm photons. What is the energy gap between the ground state and excited state in the laser material?

E= 3.82 × J

Explanation:

The energy gap between the ground state and the excited state in the laser material is equal to the energy of single 521 nm photons emitted when a single electron relaxes from the excited to ground state, i.e.

E=hf

f = c / λ   so

E = h  c  / λ

where,

h= plank constant= 6.626 × J s

c = speed of light= 3.00 × m/s

λ = wavelength of emitted photons= 521 × m

E =  6.626× × 3.00× / 521×

E= 3.82 × J