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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): The positively charged nucleus of an atom has a radius of almost 10-15m.

Reason (R): In $\alpha$-particle scattering experiment, the distance of closest approach for $\alpha$-particles is 10-15m.

✓

Answer

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

Explanation:

In $\alpha$-particle scattering experiment, Rutherford found a small number of $\alpha$-particles which were scattered back through an angle approaching to 180º. This is possible only if the positive charges are concentrated at the centre or nucleus of the atom.

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