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

Concept Questions :-

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

Concept Questions :-

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) ${n}^{2}$

Concept Questions :-

Bohr's model of atom
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The Bohr model of atoms [2004]

(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

Concept Questions :-

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

Concept Questions :-

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 $\mu m$

Concept Questions :-

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
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Consider an electron in the nth orbit of a hydrogen atom in the Bohr model. The circumference of the orbit can be expressed in terms of the de-Broglie wavelength $\lambda$ of that electron as:

(1) (0.529) n$\lambda$           (2) $\sqrt{n\lambda }$             (3) (13.6) $\lambda$         (4) n$\lambda$

Concept Questions :-

Bohr's model of atom
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In the Bohr's model of a hydrogen atom, the centripetal force is furnished by the Coulomb attraction between the proton and the electron.  If ${\alpha }_{0}$ is the radius of the ground state orbit, m is the mass and e is the charge on the electron, ${\epsilon }_{0}$ is the vaccum permittivity, the speed of the electron is  [1998]

(1) zero          (2) $\frac{e}{\sqrt{{\epsilon }_{0}{a}_{0}m}}$           (3) $\frac{e}{\sqrt{4{\mathrm{\pi \epsilon }}_{0}{\mathrm{a}}_{0}\mathrm{m}}}$               (4) $\frac{\sqrt{4{\mathrm{\pi \epsilon }}_{0}{\mathrm{a}}_{0}\mathrm{m}}}{e}$

Concept Questions :-

Bohr's model of atom
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