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MCQ practice · SSC Physics Board questions · Chapter 13: Radioactivity and Electronics

Sylhet Board 2021

Scientists came to understand that atoms:

  1. i. are in fact not indestructible
  2. ii. can break apart and give off radioactive radiation
  3. iii. will radiate their energy and fall into the nucleus

Think it through first, then pick an option.

  1. a i and ii
  2. b i and iii
  3. c ii and iii
  4. d i, ii and iii
Answer and explanation

Correct answer: a i and ii

i and ii: an unstable nucleus changes by giving off radiation, so an atom is not indestructible. iii is not true, because in the book the electrons keep moving around the nucleus and nothing says they fall inside.

Why the other options are wrong

  • b i and iii: i and iii: i is true, but iii is not: in the book electrons keep moving around the nucleus and do not fall in. And ii is true but has been left out.
  • c ii and iii: ii and iii: ii is true, but iii is not, because the book says nothing about electrons falling into the nucleus. And i is true but has been left out.
  • d i, ii and iii: i, ii and iii: iii is not true. In radioactivity it is the nucleus that gives off radiation; the electrons do not fall into the nucleus.