The electron energy in hydrogen atom is given by E = (-21.7 $$\times$$ 10^-12)/n² ergs. Calculate the energy required to remove an electron completely from the n = 2 orbit. What is the longest wavelength (in cm) of light that can be used to cause this transition?

Calculate the wavelength in Angstrom of the photon that is emitted when an electron in the Bohr orbit, n = 2 returns to the orbit, n = 1 in the hydrogen atom. The ionization potential of the ground state hydrogen atom is 2.17 $$\times$$ 10^-11 erg per atom.

The energy of the electron in the second and the third Bohr's orbits of the hydrogen atom is -5.42 $$\times$$ 10^-12 erg and -2.41 $$\times$$ 10^-12 erg respectively. Calculate the wavelength (in Å) of the emitted radiation when the electron drops from the third to second orbit.