# Photons of wavelength 4000  ${A}^{o}$ are used to break ${\mathrm{l}}_{2}$ molecules. The percentage of energy converted to the kinetic energy of atoms will be : (bond dissociation energy of the molecule is 246.5 kJ/mol) 1.  12% 2.  8% 3.  26% 4.  17%

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A photon with an initial frequency of $$10^{11}~\mathrm{Hz}$$ scatters off an electron at rest. Its final frequency is $$0.9 \times10^{11}~\mathrm{Hz}.$$ The speed of scattered electron is close to:

 1 $$3 \times10^{2}~\mathrm{ms}^{-1}$$ 2 $$3.8 \times10^{3}~\mathrm{ms}^{-1}$$ 3 $$2 \times10^{6}~\mathrm{ms}^{-1}$$ 4 $$30~\mathrm{ms}^{-1}$$



Subtopic:  Photo Electric Effect |
64%
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In the transition of an electron in an atom, its kinetic energy changes from y to $\frac{y}{4}$. The change in potential energy will be -

1. $$\frac{-3}{8} y$$
2. $${{3}\over{2}}y$$
3. $${{3}\over{4}}y$$
4. $$-{{3}\over{4}}y$$

Subtopic:  Bohr's Theory |
58%
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The wavelength of the spectral line obtained in the spectrum of ${\mathrm{Li}}^{+2}$
when the transition takes place between levels whose sum is 4 and the difference is 2, will be:

1.  11.4 x ${10}^{-6}$ cm

2.  1.14 x ${10}^{-6}$cm

3.  0.114 x ${10}^{-6}$ cm

4.  1.14 x ${10}^{-8}$ cm

Subtopic:  Hydrogen Spectra |
62%
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The charge on the electron and proton are reduced to $\frac{2}{3}\mathrm{rd}$ of their original values. Let the present value of the Rydberg constant of H-atom be R, then the new value of the Rydberg constant will be

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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In a subshell, if the number of radial nodes is two times the number of angular nodes, then the minimum possible value of the principal quantum number (n) is:

[angular nodes are non-zero)

 1 1 2 2 3 3 4 4
Subtopic:  Nodal Plane |
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The number of unpaired electrons in 1s2 2s2 2p3 is -

1. 2

2. 0

3. 3

4. 1

Subtopic:  Pauli's Exclusion Principle & Hund's Rule |
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${\mathrm{Be}}^{3+}$ion and a proton are accelerated by the same potential. The ratio of their de-Broglie wavelengths is

(assume mass of proton =  mass of neutron)

1. 1:2

2. 1:4

3. 1:1

4. 1:$3\sqrt{3}$

Subtopic:  Bohr's Theory |
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 Assertion (A): All d orbitals are tetra-lobed structures having two nodal planes. Reason (R): Out of five, only four d-orbitals are degenerate orbitals.

 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 Both (A) and (R) are false.

Subtopic:  Shell & Subshell |
51%
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