CBSE Class 12 Physics Modern Physics Exam Notes

CBSE Class 12 Physics Modern Physics Exam Notes. Please refer to the examination notes which you can use for preparing and revising for exams. These notes will help you to revise the concepts quickly and get good marks.

Bohr’s Model for atom
Bohr’s theory is a combination of classical and quantum approach. It removes the draw backs of Rutherford’s model according to which electron should loose energy while revolving around nucleus and finally should fall into nucleus. When electron goes from orbit to another it can orbit or radiate electromagnetic radiation. Postulates
(i) electron moves in circular path around nucleus under the influence of electrostatic attraction between electron and nucleus.
(ii) electron can move only in selected orbits in which electron can have angular momentum integer multiply of .h/2π
i.e., mvr = nh/2π
where h is plank’s constant and n is shell no.

Interpretation of hydrogen spectrum

The electron in the hydrogen atom resides in the first orbit. When energy is supplied, the electron moves to higher energy shells depending on the amount of energy absorbed. When this electron returns to any of the lower energy level, it emits energy. Lyman series is obtained when the electron returns to the lowest energy state while Balmer series is obtained
when the electron returns to second energy shell. Similarly, Pashcen, Brackett and Pfund series are obtained when electron returns to the third, fourth and fifth energy shell from higher energy shells respectively.

Modern Physics MCQ Questions with Answers Class 12 Physics 

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