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In the Bohr model of $$\mathrm{H\text-}$$atom, an electron $$(e)$$ is revolving around a proton $$(p)$$ with velocity $$v$$. If $$r$$ is the radius of the orbit, $$m$$ is the mass and $$\varepsilon_0$$ is vacuum permittivity, then the value of $$v$$ is:
1. $$\frac{e}{\sqrt{4\pi m\varepsilon_0 r}}$$
2. $$\frac{2e}{\sqrt{\pi m\varepsilon_0 r}}$$
3. $$\frac{e}{\sqrt{\pi m\varepsilon_0 r}}$$
4. $$\frac{e}{4\pi m\varepsilon_0 r}$$

Subtopic: Â Bohr's Model of Atom |
Â 72%
From NCERT
AIPMT - 1998
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Maximum frequency of emission is obtained for the transition:

1. n = 2 to n = 1

2. n = 6 to n = 2

3. n = 1 to n = 2

4. n = 2 to n = 6

Subtopic: Â Bohr's Model of Atom |
Â 58%
From NCERT
AIPMT - 2000
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The life span of atomic hydrogen is:

1. Fraction of one sec

2. One year

3. One hour

4. One day

Subtopic: Â Bohr's Model of Atom |
Â 81%
From NCERT
AIPMT - 2000
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When an electron transitions from $$n=4$$ to $$n=2$$, then the emitted line in the spectrum will be:
 1 the first line of the Lyman series. 2 the second line of the Balmer series. 3 the first line of the Paschen series. 4 the second line of the Paschen series.

Subtopic: Â Spectral Series |
Â 86%
From NCERT
AIPMT - 2000
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If the energy of the hydrogen atom in $$n^{\text{th}}$$ orbit is $$E_n,$$ then the energy in $$n^{\text{th}}$$ orbit of the singly ionised helium atom will be:
 1 $$4E_n$$ 2 $$\dfrac{E_n}{4}$$ 3 $$2E_n$$ 4 $$\dfrac{E_n}{2}$$
Subtopic: Â Bohr's Model of Atom |
Â 75%
From NCERT
AIPMT - 2001
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An electron is moving around the nucleus of a hydrogen atom in a circular orbit of radius $$r$$. What is the coulomb force $$\vec {F}$$ between the two? $$\left ( \text{where},K=\frac{1}{4\pi \epsilon _{0}} \right )$$
1. $$K \frac{e^{2}}{r^{2}} \hat{r}$$
2. $$- K \frac{e^{2}}{r^{3}} \hat{r}$$
3. $$K \frac{e^{2}}{r^{3}} \overset{\rightarrow}{r}$$
4. $$- K \frac{e^{2}}{r^{3}} \overset{\rightarrow}{r}$$
Subtopic: Â Various Atomic Models |
Â 53%
From NCERT
AIPMT - 2003
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In which of the following systems will the radius of the first orbit ($$n=1$$) be minimum:
1. doubly ionized lithium
2. singly ionized helium
3. deuterium atom
4. hydrogen atom

Subtopic: Â Bohr's Model of Atom |
Â 71%
From NCERT
AIPMT - 2003
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Energy $$E$$ of a hydrogen atom with principal quantum number $$n$$ is given by $$E=-\frac{13.6}{n^{2}}~\text{eV}.$$ The energy of a photon ejected when the electron jumps from $$n=3$$ state to $$n=2$$ state of hydrogen is approximately:
1. $$0.85~\text{eV}$$
2. $$3.4~\text{eV}$$
3. $$1.9~\text{eV}$$
4. $$1.5~\text{eV}$$

Subtopic: Â Bohr's Model of Atom |
Â 77%
From NCERT
AIPMT - 2004
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The Bohr model of atoms:
 1 uses Einstein's photoelectric equation. 2 predicts continuous emission spectra for atoms. 3 predicts the same emission spectra for all types of atoms. 4 assumes that the angular momentum of electrons is quantized.
Subtopic: Â Bohr's Model of Atom |
Â 80%
From NCERT
AIPMT - 2004
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The total energy of an electron in the first excited state of a hydrogen atom is about $$-3.4$$ eV. Its kinetic energy in this state will be:
1. $$-6.8~\text{eV}$$
2. $$3.4~\text{eV}$$
3. $$6.8~\text{eV}$$
4. $$-3.4~\text{eV}$$

Subtopic: Â Bohr's Model of Atom |
Â 83%
From NCERT
AIPMT - 2005
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