This is a twentieth chapter of the book Physics 12 published by Punjab Curriculum and Textbook Board, Lahore, Pakistan.
After studying this chapter, the students will be able to:
Know experimental facts of hydrogen spectrum.
Describe Bohr's postulates of hydrogen atom.
Explain hydrogen atom in terms of energy levels.
Describe de-Brogile•s interpretation of Bohr's orbits.
Understand excitation and ionization potentials.
Describe uncertainty regarding position of electron in the atom.
Understand the production, properties and uses of X-rays.
Describe the terms spontaneous emission, stimulated emission, metastable state and population inversion.
Understand laser principle.
Describe the He-Ne gas laser.
Describe the application of laser including holography.