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The de-Broglie wavelength of an electron in the ground state of the \(\mathrm{H\text-}\)atoms is \(\lambda_1,\) while that in the \(\mathrm{He}^+\) ion is \(\lambda_2.\) The ratio \(\dfrac{\lambda_1}{\lambda_2}\) is:
1. \(4\) 2. \(2\)
3. \(\dfrac12\) 4. \(\dfrac14\)

Subtopic:  Bohr's Model of Atom |
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Light having the wavelength equal to the first line of the Lyman series is incident on a metal having a work function of \(6\) eV. The energy of the fastest photo-electron emitted is:
1. \(7.6\) eV
2. \(4.2\) eV
3. \(2.1\) eV
4. \(0.8\) eV
Subtopic:  Spectral Series |
 66%
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What is the minimum voltage required to be applied to a Coolidge tube to generate \(X\)-rays of wavelength \(0.5~\mathring{A}?\) \((h=12.4~\text{keV-}\mathring{A}/c)\)
1. \(12.4\) kV
2. \(6.2\) kV
3. \(24.8\) kV
4. \(37.2\) kV
 64%
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Given below are two statements: 
Statement I: The time period of revolution of an electron in its \(n^\mathrm{th}\) Bohr orbit in an atom is directly proportional to \(n^3.\)
Statement II: The kinetic energy of an electron in its \(n^\mathrm{th}\) Bohr orbit in an atom is directly proportional to \(n.\)
 
1. Statement I is incorrect and Statement II is correct.
2. Both Statement I and Statement II are correct.
3. Both Statement I and Statement II are incorrect.
4. Statement I is correct and Statement II is incorrect.
Subtopic:  Bohr's Model of Atom |
 82%
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The product of the angular momentum and the kinetic energy of an electron in the \(n^\text{th}\) Bohr orbit in a hydrogen atom is proportional to:
1. \(n\)
2. \(n^2\)
3. \(\dfrac1n\)
4. \(\dfrac{1}{n^3}\)
Subtopic:  Bohr's Model of Atom |
 78%
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The electrostatic potential at the location of an electron in the ground state of the \(\mathrm{H}\)-atom is:
1. \(13.6~\text V\)
2. \(6.8~\text V\) 
3. \(27.2~\text V\) 
4. \(3.4~\text V\) 
Subtopic:  Bohr's Model of Atom |
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Given below are two statements: 
Statement I: The stationary orbits in Bohr's theory correspond to those orbits in which an integer number of de-Broglie wavelengths of the orbiting electron fit in.
Statement II: Photons having an energy greater than \(13.6~\text{eV}\) cannot be absorbed by an \(\mathrm{H}\)-atom in the ground state.
 
1. Statement I is incorrect and Statement II is correct.
2. Both Statement I and Statement II are correct.
3. Both Statement I and Statement II are incorrect.
4. Statement I is correct and Statement II is incorrect.
Subtopic:  Bohr's Model of Atom |
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Light, having a wavelength equal to the first line of the Balmer series, is incident onto a metal of work-function \(2\) eV. The kinetic energy of the ejected electron is:
1. \(1.4\) eV
2. \(0.5\) eV
3. \(0.1\) eV
4. no electrons are ejected
Subtopic:  Bohr's Model of Atom |
 64%
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In an experiment of \(\alpha\)-particle scattering by a gold foil (Geiger-Marsdon experiment), the \(\alpha\)-particles have kinetic energy \((KE=1.2\times 10^{-12}~\text J).\) What is the approximate distance of the closest approach of the \(\alpha\)-particles to the gold nuclei?
(take \(Z_\text{gold}=79\) )
1. \(3\times 10^{-14}~\text m\)
2. \(3\times 10^{-13}~\text m\)
3. \(3\times 10^{-12}~\text m\)
4. \(3\times 10^{-11}~\text m\)
Subtopic:  Various Atomic Models |
 70%
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An electron in an \(\mathrm{H}\text-\)atom makes a transition from the ground state into another state where its de-Broglie wavelength is doubled. The energy required to make this transition is:
1. \(13.6~\text{eV}\)
2. \(10.2~\text{eV}\)
3. \(12.75~\text{eV}\)
4. \(12.1~\text{eV}\)
Subtopic:  Bohr's Model of Atom |
 71%
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