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JEE Main Atoms — practice questions

Explore 6 free Atoms questions in JEE Main 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 1–6 of 6.

Bohr's postulate quantises the angular momentum of an electron in a stationary orbit asRead the answer and worked solution →Which spectral series of hydrogen lies in the visible region of the electromagnetic spectrum?Read the answer and worked solution →The minimum wavelength $\lambda_{\min}$ in the continuous X-ray spectrum of an X-ray tube depends only onRead the answer and worked solution →The ratio of the longest wavelength in the Lyman series to the longest wavelength in the Balmer series of hydrogen isRead the answer and worked solution →The radius of the $n$th Bohr orbit in a hydrogen-like atom of nuclear charge $Z$ scales asRead the answer and worked solution →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 →

Worked practice questions

Bohr's postulate quantises the angular momentum of an electron in a stationary orbit as

  1. $L = \tfrac{\hbar}{n}$
  2. $L = nh^2$
  3. $L = n\hbar$
  4. $L = nh$
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Correct answer: C. $L = n\hbar$

Bohr postulated $L = mvr = n\hbar = \tfrac{nh}{2\pi}$ for positive integers $n$. **Option A is off by a factor of $2\pi$ — a classic distractor.**

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Which spectral series of hydrogen lies in the visible region of the electromagnetic spectrum?

  1. Paschen
  2. Pfund
  3. Lyman
  4. Balmer
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Correct answer: D. Balmer

Balmer (transitions to $n=2$) covers wavelengths roughly $364\,\text{nm}$ to $656\,\text{nm}$ — the visible band. Lyman is UV (transitions to $n=1$), Paschen and Pfund are infrared (to $n=3$ and $n=5$).

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The minimum wavelength $\lambda_{\min}$ in the continuous X-ray spectrum of an X-ray tube depends only on

  1. the type of cathode
  2. the target material
  3. the accelerating voltage
  4. the filament current
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Correct answer: C. the accelerating voltage

$\lambda_{\min} = \tfrac{hc}{eV}$, where $V$ is the accelerating voltage. The cutoff is purely a kinematic limit set by how much energy a single electron can convert to a photon. Target material affects the *characteristic* lines, not the continuous cutoff.

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More Physics topics

Electric Charges and FieldsMechanical Properties of Solids and FluidsSemiconductor ElectronicsWave OpticsCurrent ElectricityUnit 2A: Newton's Laws and Translational EquilibriumMoving Charges and MagnetismAtoms and Nuclei