How does the Bohr's model of the atom explain line-emission spectra?
Bohr's model shows a hypothetical energy level, or quanta, at each energy state. When energy is applied to an electron surrounding a hydrogen atom it goes into an excited state. However, in physical science you learn that the universe tends to go to the lowest possible energy state, so when the electron goes back to its "ground state" it gives off energy, and that energy is evident as light that can be measured.
You can measure the wavelengths of these excited phases using the Rydberg equation
Where R is the Rydberg Constant (1.09E7)
n' is the ground state and n is the excited state.