In terms of Bohr radius ${a}_{0}$, the radius of the second Bohr orbit of a hydrogen atom is given by 

(1) 4${a}_{0}$              (2) 8${a}_{0}$           (3) $\sqrt{2}$${a}_{0}$              (4) 2${a}_{0}$

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Bohr's model of atom
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The energy of lowest state of hydrogen is -13.6 eV. The ionisation energy of first excited state will be

1. 13.6 eV                             2. 4.2 eV

3. 6.8 eV                               4. 3.4 eV

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Bohr's model of atom
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An x-ray tube is operating at 30 kV then the minimum wavelength of the x-rays coming out of the tube is:

(1) 1.24 $\stackrel{0}{A}$          (2) 0.413 $\stackrel{0}{A}$             (3) 0.124 $\stackrel{0}{A}$             (4) 0.13 $\stackrel{0}{A}$

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X-ray
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A diatomic molecule is made of two masses  which are separated by a distance r.  If we calculate its rotational energy by applying Bohr's rule of angular momentum quantization, its energy will be given by (n is an integer):

(1) $\frac{{\left({m}_{1}+{m}_{2}\right)}^{2}{n}^{2}{h}^{2}}{2{m}_{1}^{2}{m}_{2}^{2}{r}^{2}}$                   (2) $\frac{{n}^{2}{h}^{2}}{2{\mathrm{\pi }}^{2}\left({m}_{1}^{}+{m}_{2}^{}\right){r}^{2}}$

(3) $\frac{2{n}^{2}{h}^{2}}{\left({m}_{1}^{}+{m}_{2}^{}\right){r}^{2}}$                           (4) $\frac{\left({m}_{1}+{m}_{2}\right){n}^{2}{h}^{2}}{8{\mathrm{\pi }}^{2}{m}_{1}^{}{m}_{2}^{}{r}^{2}}$

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Bohr's model of atom
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In a hydrogen atom, which of the following electronic transitions would involve the maximum energy change ?

(A) From n = 2 to n = 1

(B) From n = 3 to n = 1

(C) From n = 4 to n = 2

(D) From  n = 3 to n = 2

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Bohr's model of atom
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In the Bohr's hydrogen atom model, the radius of the stationary orbit is directly proportional to (n = principal quantum number) [CBSE PMT 1996; AIIMS 199; DCE 2002; AMU (med.) 2010)

(1) ${n}^{-1}$        (2) n            (3) ${n}^{-2}$         (4) ${n}^{2}$

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Bohr's model of atom
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The Bohr model of atoms 

(1) assumes that the angular momentum of electrons is quantised

(2) uses Einstein's photoelectric equation

(3) Predicts continuous emission spectra for atoms

(4) Predicts the same emission spectra for all types of atoms

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Bohr's model of atom
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When a hydrogen atom is raised from the ground state to excited state

(1) both KE and PE increase

(2) both KE and PE decrease

(3) PE increases and KE decreases

(4) PE decreases and KE increases

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Bohr's model of atom
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The extreme wavelengths of Paschen series are

(1) 0.365 $\mu m$ and 0.565 $\mu m$

(2) 0.818 $\mu m$ and 0.189 $\mu m$

(3) 1.45 $\mu m$ and 4.04 $\mu m$

(4) 2.27 $\mu m$ and 7.43 $\mu m$

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Spectral series
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A hydrogen atom is in an excited state of principal quantum number (n), it emits a photon of wavelength ($\lambda$) when it returns to the ground state. The value of n is

(1) $\sqrt{\frac{\lambda R}{\lambda R-1}}$                   (2) $\sqrt{\frac{\left(\lambda R-1\right)}{\lambda R}}$

(3) $\sqrt{\lambda \left(R-1\right)}$                   (4) None of these

Concept Questions :-

Bohr's model of atom