A dye absorbs a photon of wavelength $\mathrm{\lambda }$ and re-emits the same energy into two photons of wavelengths ${\mathrm{\lambda }}_{1}$  and ${\mathrm{\lambda }}_{2}$ respectively. The wavelength $\mathrm{\lambda }$ is related to ${\mathrm{\lambda }}_{1}$ and ${\mathrm{\lambda }}_{2}$ as:

1.  $\mathrm{\lambda }=\frac{{\mathrm{\lambda }}_{1}+{\mathrm{\lambda }}_{2}}{{\mathrm{\lambda }}_{1}{\mathrm{\lambda }}_{2}}$

2.  $\mathrm{\lambda }=\frac{{\mathrm{\lambda }}_{1}{\mathrm{\lambda }}_{2}}{{\mathrm{\lambda }}_{1}+{\mathrm{\lambda }}_{2}}$

3.  $\mathrm{\lambda }=\frac{{\mathrm{\lambda }}_{1}^{2}+{\mathrm{\lambda }}_{2}^{2}}{{\mathrm{\lambda }}_{1}+{\mathrm{\lambda }}_{2}}$

4.  $\mathrm{\lambda }=\frac{{\mathrm{\lambda }}_{1}{\mathrm{\lambda }}_{2}}{{\left({\mathrm{\lambda }}_{1}+{\mathrm{\lambda }}_{2}\right)}^{2}}$

Subtopic:  Bohr's Theory |
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The energy of an electron in the first Bohr's orbit of an H-atom is -13.6 eV. The possible energy value (s) of the excited state(s) for electrons in Bohr's orbits of hydrogen is (are):

1. -3.4 eV

2. -4.2 eV

3. -6.8 eV

4. +6.8 eV

Subtopic:  Bohr's Theory |
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 Assertion (A): The angular momentum of an electron in an atom is quantized. Reason (R): In an atom, only those orbits are permitted in which the angular momentum of the electron is a natural number multiple of h/2π.

 1 Both (A) and (R) are True and (R) is the correct explanation of (A). 2 Both (A) and (R) are True but (R) is not the correct explanation of (A). 3 (A) is True but (R) is False. 4 (A) is False but (R) is True.
Subtopic:  Bohr's Theory |
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For any H-like system, the ratio of velocities of I, II & III orbit i.e.,  will be:

1.  1 : 2 : 3

2.  1 : 1/2 : 1/3

3.  3 : 2 : 1

4.  1 : 1 : 1

Subtopic:  Bohr's Theory |
73%
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The concept that contradicts the Bohr Model of an atom is:

 1 Rutherford Model 2 Heisenberg's Uncertainty Principle 3 J.J. Thomson Model 4 Photoelectric Effect

Subtopic:  Bohr's Theory |
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An ion among the following that has the same radius as a hydrogen atom, having n=1, is

1. ${\mathrm{He}}^{+},$ $n=2$

2. ${\mathrm{Li}}^{2+},n=2$

3. ${\mathrm{Be}}^{3+},$ $n=2$

4. ${\mathrm{Li}}^{2+},\mathrm{n}=3$

Subtopic:  Bohr's Theory |
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 Assertion (A): Bohr’s orbits are also called stationary states. Reason (R): Electrons are stationary in an orbit.

 1 Both (A) and (R) are true and (R) is the correct explanation of (A). 2 Both (A) and (R) are true but (R) is not the correct explanation of (A). 3 (A) is true but (R) is false. 4 (A) is false but (R) is true.

Subtopic:  Bohr's Theory |
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 Assertion (A): The radius of the second orbit of He+ is equal to that of the first orbit of hydrogen. Reason (R): The radius of an orbit in hydrogen-like species is directly proportional to n and inversely proportional to Z.

 1 Both  (A) and (R) are True and (R) is the correct explanation of the (A). 2 Both (A) and (R) are True and (R) is not the correct explanation of the (A). 3 (A) is True but (R) is False. 4 Both (A) and (R) are False.
Subtopic:  Bohr's Theory |
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If the size of the first orbit of the hydrogen atom is 5.29 nm, the size of the second orbit of He+ is

1. 2.65 nm

2. 21.16 nm

3. 10.58 nm

4. 5.29 nm

Subtopic:  Bohr's Theory |
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The wavelength of a certain line in the Balmer series is observed to be 4341 Afor hydrogen atoms.
The electronic transition among the following may be:

1. 3 → 2
2. 4 → 1
3. 5 → 2
4. 5 → 3

Subtopic:  Bohr's Theory |
58%
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