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Atoms — Physics STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 SciencePhysicsAtoms1 Mark
Question
For question two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is NOT the correct explanation of A.
  3. A is true, but R is false.
  4. A is false and R is also false.
Assertion (A): Between any two given energy levels, the number of absorption transitions is always less than the number of emission transitions.
Reason (R): Absorption transitions start from the lowest energy level only and may end at any higher energy level. But emission transitions may start from any higher energy level and end at any energy level below it.
✓

Answer

  1. Both A and R are true, and R is the correct explanation of A.
Explanation:

Absorption transition



Two possibilities in absorption transition. Emission transition



Three possibilities in emission transition. Therefore, number of absorption transition < number of emission transition. For any two states A and B such that $E_A < E_8$ we have absorption spectrum for A → B transition and emission B → A. But most of the time atoms are in ground state, absorption is only from the ground state.

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