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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): Balmer series lies in the visible region of electromagnetic spectrum.

Reason (R): $\frac{1}{\lambda}=\text{R}\Big(\frac{1}{2^2}-\frac{1}{\text{K}^2}\Big)$, where K = 3, 4, 5, ...

✓

Answer

  1. Both A and R are true, but R is NOT the correct explanation of A.

Explanation:

When we put R = 107m-1 and K = 3, 4 5, in the given formula, values of $\lambda$ calculated lie between 4000A and 8000A, which is the visible region. The reason is true, but does not explain the assertion properly.

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