The ratio of the longest to shortest wavelengths in Lyman series of hydrogen spectra is [EAMCET (Med.) 2000; BCECE 2006; J & K CET 2006]

(1) $\frac{25}{9}$            (2) $\frac{17}{6}$         (3) $\frac{9}{5}$          (4) $\frac{4}{3}$

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Spectral series
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Hydrogen atoms are excited from ground state of the principal quantum number 4. Then, the number of spectral lines observed will be

(a) 3                                     (b) 6

(c) 5                                     (d) 2

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Spectral series
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When electron jumps from n = 4 to n = 2 orbit, we get [2000]

(1) second line of Lyman series

(2) second line of Balmer series

(3) second line of Paschen series

(4) an absorption line of Balmer series

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Spectral series
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The spectrum obtained from a sodium vapour lamp is an example of

(a) band spectrum

(b) continuous spectrum

(c) emission spectrum

(d) absorption spectrum

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Spectral series
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The radius of hydrogen atom in its ground state is  After collision with an electron it is found to have a radius of 21.2 $×{10}^{-11}$ m. What is the principal quantum number n of the final state of the atom? [1994]

(1) n = 4            (2) n = 2            (3) n = 16            (4) n = 3

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Bohr's model of atom
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In terms of Bohr radius ${a}_{0}$, the radius of the second Bohr orbit of a hydrogen atom is given by [1992]

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

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