Chapter 20: Atomic Spectra

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.