In a Geiger-Marsden experiment, what is the distance of the closest approach to the nucleus of a \(7.7\) MeV \(\alpha\)-particle before it comes momentarily to rest and reverses its direction?
1. \(10\) fm

2. \(25\) fm

3. \(30\) fm

4. \(35\) fm

Subtopic:  Various Atomic Models |
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When an \(\alpha\text-\)particle of mass \(m\) moving with velocity \(v\) bombards on a heavy nucleus of charge \(Ze\), its distance of closest approach from the nucleus depends on \(m\) as:
1. \(\frac{1}{\sqrt{m}}\)
2. \(\frac{1}{m^{2}}\)
3. \(m\)
4. \( \frac{1}{m}\)
Subtopic:  Various Atomic Models |
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NEET - 2016
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It is found experimentally that \(13.6~\text{eV}\) energy is required to separate a hydrogen atom into a proton and an electron. The velocity of the electron in a hydrogen atom is:
1. \(3.2\times10^6~\text{m/s}\)
2. \(2.2\times10^6~\text{m/s}\)
3. \(3.2\times10^6~\text{m/s}\)
4. \(1.2\times10^6~\text{m/s}\)

Subtopic:  Various Atomic Models |
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Given below are two statements: 
Statement I: The time period of revolution of an electron in its \(n^\text{th}\) Bohr orbit in an atom is directly proportional to \(n^3.\)
Statement II: The K.E of an electron in its \(n^\text{th}\) 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 |
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According to the classical electromagnetic theory, the initial frequency of the light emitted by the electron revolving around a proton in the hydrogen atom is: (The velocity of the electron moving around a proton in a hydrogen atom is \(2.2\times10^{6}\) m/s)

1. \(7.6\times10^{13}\) Hz 2. \(4.7\times10^{15}\) Hz
3.  \(6.6\times10^{15}\) Hz 4. \(5.2\times10^{13}\) Hz
Subtopic:  Bohr's Model of Atom |
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An electron in hydrogen atom makes a transition \(n_1 \rightarrow n_2\) where \(n_1\) and \(n_2\) are principal quantum numbers of the two states. Assuming Bohr's model to be valid, the time period of the electron in the initial state is eight times that in the final state. The possible values of \(n_1\) and  \(n_2\) are:
1. \( n_1 = 6~\text{and}~n_2 = 2\)
2. \( n_1 = 8~\text{and}~ n_2 = 1\)
3. \( n_1 = 8~\text{and}~ n_2 = 2\)
4. \(n_1 = 4~\text{and}~n_2 = 2\)
Subtopic:  Bohr's Model of Atom |
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From NCERT
NEET - 2013
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A \(10~\text{kg}\) satellite circles earth once every \(2~\text{h}\) in an orbit having a radius of \(8000~\text{km}\). Assuming that Bohr’s angular momentum postulate applies to satellites just as it does to an electron in the hydrogen atom. The quantum number of the orbit of the satellite is:
1. \(2.0\times10^{43}\)
2. \(4.7\times10^{45}\)
3. \(3.0\times10^{43}\)
4. \(5.3\times10^{45}\)

Subtopic:  Bohr's Model of Atom |
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Let \(T_1\) and \(T_2\) be the energy of an electron in the first and second excited states of hydrogen atom, respectively. According to Bohr's model of an atom, the ratio \(T_1:T_2\) is:
1. \(9:4\)
2. \(1:4\)
3. \(4:1\)
4. \(4:9\) 
Subtopic:  Bohr's Model of Atom |
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NEET - 2022
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The minimum orbital angular momentum of the electron in a hydrogen atom is:
1. \(h\)
2. \(h/2\)
3. \(h/2\pi\)
4. \(h/ \lambda\)

Subtopic:  Bohr's Model of Atom |
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Let \(L_1\) and \(L_2\) be the orbital angular momentum of an electron in the first and second excited states of the hydrogen atom, respectively. According to Bohr's model, the ratio \(L_1:L_2\) is:
1. \(1:2\)
2. \(2:1\)
3. \(3:2\)
4. \(2:3\)

Subtopic:  Bohr's Model of Atom |
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NEET - 2022
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