If frequency of the X-rays produced using an element as anti-cathode is found to be 2500 sec-1, the atomic number of used element is (a, b= 1)

1. 51

2. 49

3. 56

4. 72

Subtopic:  Introduction of Atomic Structure |
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What is the energy required per mole to excite an electron from the third to fifth Bohr orbit in hydrogen ?

1. 6.336 x 106J

2. 7.122 x 104J

3. 0.343 x 106J

4. 9.343 x 104J

Subtopic:  Bohr's Theory |
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The energy of electron in first Bohr's orbit of H-atom is -13.6 eV. What will be its potential energy in n = 4.

1. –13.6 eV

2. - 3.4 eV

3. -0.85 eV

4. -1.70 eV

Subtopic:  Bohr's Theory |
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Sodium atoms can be ionised by supplying an energy of 118 kcal mol-1. Using this data, calculate the lowest possible frequency of light that can ionise a sodium atom.

(h = 6.624 x 10-27 erg.sec, c= 3 x 1010 cm sec-1).

1. 1.24 x 1015 sec-1

2. 0.24 x 1015 sec-1 

3. 12.4 x 1012 sec-1

4. 2.31 x 1018 sec-1

Subtopic:  Electromagnetic Radiation |
 52%
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A glow worm of mass 5.0 g emits red light (650 nm) with a power of 0.1 W. entirely in the backward direction. What velocity would it accelerate to after 10 years, if released in free space (and assumed to be alive)?

1. 9.14 ms-1 

2. 28.08 ms-1

3. 11.05 ms-1

4. 21.04 ms-1

Subtopic:  Electromagnetic Radiation |
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Which of the following postulates does not belong to Bohr's model of the atom?

1. Angular momentum is an integral multiple of h/2π

2. The electron stationed in the orbit is stable

3. The path of an electron is circular

4. The change in the energy levels of electron is continuous

Subtopic:  Bohr's Theory |
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The total number of orbitals having l = 3  is - 

1. 3

2. 7

3. 5

4. 9

Subtopic:  Quantum Numbers & Schrodinger Wave Equation |
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Bohr's atomic model provides explanations for:

1. The spectrum of hydrogen atoms only.

2. The spectrum of an atom or ion containing only one electron.

3. The spectrum of hydrogen molecule.

4. The solar spectrum.

Subtopic:  Bohr's Theory |
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The presence of one electron each in the three 2p sub-shell of nitrogen is explained by 

1. Uncertainty principle

2. Hund's rule

3. Pauli's principle 

4. Bohr's theory

Subtopic:  Pauli's Exclusion Principle & Hund's Rule |
 77%
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When the atoms of gold sheet are bombarded with a beam of α -particles, only a few a-particles get deflected where as most of them go straight undeflected. This is because:

1. The force of attraction on the α-particles by the oppositely charged electron is not sufficient.
2. The nucleus occupies much smaller volume as compared to the volume of atom.
3. The force of repulsion on fast moving α-particles is very small.
4. The neutrons in the nucleus do not have any effect on α-particles.

Subtopic:  Introduction of Atomic Structure |
 83%
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