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Indian Navy SSR (Sailor) Atoms — practice questions

Explore 24 free Atoms questions in Indian Navy SSR (Sailor) Physics. Open each question or exercise to read its content, reference answers and available explanation.

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Atoms questions and exercises with answers

Showing questions 1–24 of 24.

The de Broglie wavelength $\lambda$ of an electron in the $n$th Bohr orbit of hydrogen, in terms of the orbit radius $r_n$, isRead the answer and worked solution →Order the atomic models in this chapterRead the answer and worked solution →True or false: Rutherford's two difficultiesRead the answer and worked solution →Which model does this belong to?Read the answer and worked solution →Complete Bohr's first postulateRead the answer and worked solution →True or false: line spectraRead the answer and worked solution →Charge and neutralityRead the answer and worked solution →Assertion and reasonRead the answer and worked solution →Two are true, one is notRead the answer and worked solution →Three of these are wrong. Find the one that holds.Read the answer and worked solution →Tap every problem Bohr's model was built to solveRead the answer and worked solution →Flip and pair: model with its pictureRead the answer and worked solution →Spot the one that does not belongRead the answer and worked solution →Strength or weakness?Read the answer and worked solution →Complete the size of the nucleusRead the answer and worked solution →Reading the models backRead the answer and worked solution →Bohr's postulatesRead the answer and worked solution →Explained, or left unexplained?Read the answer and worked solution →True or false: the nucleusRead the answer and worked solution →Order the argument: why Rutherford's atom should collapseRead the answer and worked solution →Two are true, one is notRead the answer and worked solution →Assertion and reason: modelsRead the answer and worked solution →Spot the one that does not belongRead the answer and worked solution →Flip and pair: problem with the model that solved itRead the answer and worked solution →

Worked practice questions

The de Broglie wavelength $\lambda$ of an electron in the $n$th Bohr orbit of hydrogen, in terms of the orbit radius $r_n$, is

  1. $\lambda = 2\pi n r_n$
  2. $\lambda = \tfrac{2\pi r_n}{n}$
  3. $\lambda = n r_n$
  4. $\lambda = \tfrac{r_n}{n}$
Show answer and solution

Correct answer: B. $\lambda = \tfrac{2\pi r_n}{n}$

Bohr's stable-orbit condition is exactly the de Broglie standing-wave condition: the orbit circumference equals an integer number of wavelengths, $2\pi r_n = n\lambda$. Solving for $\lambda$ gives $\tfrac{2\pi r_n}{n}$. This is the bridge between Bohr's ad-hoc quantisation and wave mechanics.

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Order the atomic models in this chapter

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Steps
  1. Thomson: a sphere of positive charge with electrons embedded in it
  2. Rutherford: mass and positive charge concentrated in a tiny nucleus
  3. Bohr: electrons in stable stationary orbits, from three postulates
Thomson, then Rutherford, then Bohr, each answering the last one's failure. Source: syllabus Physics, Ch 12 Atoms.

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True or false: Rutherford's two difficulties

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Questions
  1. Statement is true
    Yes
    Statement
    Rutherford's model predicts atoms should be unstable.
  2. Statement is true
    Yes
    Statement
    That is because an accelerating electron would spiral into the nucleus.
  3. Statement is true
    Yes
    Statement
    It also fails to explain the line spectra of elements.
  4. Statement is true
    No
    Statement
    Rutherford's model explains line spectra well.
  5. Statement is true
    Yes
    Statement
    The nucleus is roughly one ten-thousandth the size of the atom.
The chapter names both failures explicitly. Source: syllabus Physics, Ch 12 Atoms.

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