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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): Fraunhofer lines are observed in the spectrum of the sun.

Reason (R): The different elements have different spectra.

✓

Answer

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

Explanation:

When white light from the photosphere (central portion of the sun) passes through vapours of various elements present in the outer chromosphere, then these elements absorb those wavelengths which they themselves emit to bring incandescent. Hence, dark lines (absence of light) appear in the continuous solar spectrum, due to absorption of these lines. Absorption is possible in the sun, not only from the ground state but also in higher states because of the high temperature of the sun.

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