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PHXII12:ATOMS

356535 The ground state energy of an atom is $- 217.8 e V$ . Photon emitted during the transition of electron from $n = 3$ to $n = 1$ state, is incident on a photosensitive material of unknown work function. The photoelectrons are emitted from the materials with a maximum kinetic energy of $190.29 e V$ . The threshold wavelength of the material used is
(Take $h = 6.62 \times 10^{- 34} J s$ ]

1

3750

A^{\circ}

2

1275

A^{\circ}

3

5347

A^{\circ}

4

7255

A^{\circ}

Explanation:

For transition from $n = 3$ to $n = 1$ ,
Energy of the emitted photon,
$h u = E_{3} - E_{1}$
$= [\frac{- 217.8}{3^{2}} - (\frac{- 217.8}{1^{2}})] e V$
$= [- 24.2 + 217.8] e V$
$= 193.6 e V$
From Einstein's photoelectric equation,
$h u = K_{max} + W_{0}$
$∴ W_{0} = h u - K_{max}$
$= (193.6 - 190.29) e V$
$= 3.31 e V$
$But λ_{0} = \frac{h c}{W_{0}}$
$= \frac{6.62 \times 10^{- 34} \times 3 \times 10^{8}}{3.31 \times 1.6 \times 10^{- 19}}$
$= 3.75 \times 10^{- 7} m$ ,
$= 3750$ $A^{\circ}$

PHXII12:ATOMS

356536 If elements with principal quantum number $n > 4$ were not allowed in nature, then the number of possible elements would be

1

32

2

60

3

18

4

4

Explanation:

Number of elements in an orbit having principle quantum number $n$ is $2 n^{2}$ . The total number of elements having $n < 5$ are $2 + 8 + 18 + 32 = 60$

PHXII12:ATOMS

356537 The classification of discrete energy levels in atoms was first given experimentally by

1 Thomson’s experiment

2 Millikan’s oil drop experiment

3 Frank - Hertz experiment

4 Leonard experiment

PHXII12:ATOMS

356538 Assertion :
In a metal all the free electrons are in same energy band.
Reason :
Electrons do not obey Pauli's exclusion principle.

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but reason is correct.

Explanation:

Metals are solids (except $H g$ ). They have single energy band (for carriers viz. electrons) in the sense that valence band and conduction band overlop: The band formation is any solids is due to extension of Pauli exclusion principle which is originally for atoms
$\Rightarrow$ Reason is false. So correct option is (3).

PHXII12:ATOMS

356535 The ground state energy of an atom is $- 217.8 e V$ . Photon emitted during the transition of electron from $n = 3$ to $n = 1$ state, is incident on a photosensitive material of unknown work function. The photoelectrons are emitted from the materials with a maximum kinetic energy of $190.29 e V$ . The threshold wavelength of the material used is
(Take $h = 6.62 \times 10^{- 34} J s$ ]

1

3750

A^{\circ}

2

1275

A^{\circ}

3

5347

A^{\circ}

4

7255

A^{\circ}

Explanation:

For transition from $n = 3$ to $n = 1$ ,
Energy of the emitted photon,
$h u = E_{3} - E_{1}$
$= [\frac{- 217.8}{3^{2}} - (\frac{- 217.8}{1^{2}})] e V$
$= [- 24.2 + 217.8] e V$
$= 193.6 e V$
From Einstein's photoelectric equation,
$h u = K_{max} + W_{0}$
$∴ W_{0} = h u - K_{max}$
$= (193.6 - 190.29) e V$
$= 3.31 e V$
$But λ_{0} = \frac{h c}{W_{0}}$
$= \frac{6.62 \times 10^{- 34} \times 3 \times 10^{8}}{3.31 \times 1.6 \times 10^{- 19}}$
$= 3.75 \times 10^{- 7} m$ ,
$= 3750$ $A^{\circ}$

PHXII12:ATOMS

356536 If elements with principal quantum number $n > 4$ were not allowed in nature, then the number of possible elements would be

1

32

2

60

3

18

4

4

Explanation:

Number of elements in an orbit having principle quantum number $n$ is $2 n^{2}$ . The total number of elements having $n < 5$ are $2 + 8 + 18 + 32 = 60$

PHXII12:ATOMS

356537 The classification of discrete energy levels in atoms was first given experimentally by

1 Thomson’s experiment

2 Millikan’s oil drop experiment

3 Frank - Hertz experiment

4 Leonard experiment

PHXII12:ATOMS

356538 Assertion :
In a metal all the free electrons are in same energy band.
Reason :
Electrons do not obey Pauli's exclusion principle.

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but reason is correct.

Explanation:

Metals are solids (except $H g$ ). They have single energy band (for carriers viz. electrons) in the sense that valence band and conduction band overlop: The band formation is any solids is due to extension of Pauli exclusion principle which is originally for atoms
$\Rightarrow$ Reason is false. So correct option is (3).

PHXII12:ATOMS

356535 The ground state energy of an atom is $- 217.8 e V$ . Photon emitted during the transition of electron from $n = 3$ to $n = 1$ state, is incident on a photosensitive material of unknown work function. The photoelectrons are emitted from the materials with a maximum kinetic energy of $190.29 e V$ . The threshold wavelength of the material used is
(Take $h = 6.62 \times 10^{- 34} J s$ ]

1

3750

A^{\circ}

2

1275

A^{\circ}

3

5347

A^{\circ}

4

7255

A^{\circ}

Explanation:

For transition from $n = 3$ to $n = 1$ ,
Energy of the emitted photon,
$h u = E_{3} - E_{1}$
$= [\frac{- 217.8}{3^{2}} - (\frac{- 217.8}{1^{2}})] e V$
$= [- 24.2 + 217.8] e V$
$= 193.6 e V$
From Einstein's photoelectric equation,
$h u = K_{max} + W_{0}$
$∴ W_{0} = h u - K_{max}$
$= (193.6 - 190.29) e V$
$= 3.31 e V$
$But λ_{0} = \frac{h c}{W_{0}}$
$= \frac{6.62 \times 10^{- 34} \times 3 \times 10^{8}}{3.31 \times 1.6 \times 10^{- 19}}$
$= 3.75 \times 10^{- 7} m$ ,
$= 3750$ $A^{\circ}$

PHXII12:ATOMS

356536 If elements with principal quantum number $n > 4$ were not allowed in nature, then the number of possible elements would be

1

32

2

60

3

18

4

4

Explanation:

Number of elements in an orbit having principle quantum number $n$ is $2 n^{2}$ . The total number of elements having $n < 5$ are $2 + 8 + 18 + 32 = 60$

PHXII12:ATOMS

356537 The classification of discrete energy levels in atoms was first given experimentally by

1 Thomson’s experiment

2 Millikan’s oil drop experiment

3 Frank - Hertz experiment

4 Leonard experiment

PHXII12:ATOMS

356538 Assertion :
In a metal all the free electrons are in same energy band.
Reason :
Electrons do not obey Pauli's exclusion principle.

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but reason is correct.

Explanation:

Metals are solids (except $H g$ ). They have single energy band (for carriers viz. electrons) in the sense that valence band and conduction band overlop: The band formation is any solids is due to extension of Pauli exclusion principle which is originally for atoms
$\Rightarrow$ Reason is false. So correct option is (3).

PHXII12:ATOMS

356535 The ground state energy of an atom is $- 217.8 e V$ . Photon emitted during the transition of electron from $n = 3$ to $n = 1$ state, is incident on a photosensitive material of unknown work function. The photoelectrons are emitted from the materials with a maximum kinetic energy of $190.29 e V$ . The threshold wavelength of the material used is
(Take $h = 6.62 \times 10^{- 34} J s$ ]

1

3750

A^{\circ}

2

1275

A^{\circ}

3

5347

A^{\circ}

4

7255

A^{\circ}

Explanation:

For transition from $n = 3$ to $n = 1$ ,
Energy of the emitted photon,
$h u = E_{3} - E_{1}$
$= [\frac{- 217.8}{3^{2}} - (\frac{- 217.8}{1^{2}})] e V$
$= [- 24.2 + 217.8] e V$
$= 193.6 e V$
From Einstein's photoelectric equation,
$h u = K_{max} + W_{0}$
$∴ W_{0} = h u - K_{max}$
$= (193.6 - 190.29) e V$
$= 3.31 e V$
$But λ_{0} = \frac{h c}{W_{0}}$
$= \frac{6.62 \times 10^{- 34} \times 3 \times 10^{8}}{3.31 \times 1.6 \times 10^{- 19}}$
$= 3.75 \times 10^{- 7} m$ ,
$= 3750$ $A^{\circ}$

PHXII12:ATOMS

356536 If elements with principal quantum number $n > 4$ were not allowed in nature, then the number of possible elements would be

1

32

2

60

3

18

4

4

Explanation:

Number of elements in an orbit having principle quantum number $n$ is $2 n^{2}$ . The total number of elements having $n < 5$ are $2 + 8 + 18 + 32 = 60$

PHXII12:ATOMS

356537 The classification of discrete energy levels in atoms was first given experimentally by

1 Thomson’s experiment

2 Millikan’s oil drop experiment

3 Frank - Hertz experiment

4 Leonard experiment

PHXII12:ATOMS

356538 Assertion :
In a metal all the free electrons are in same energy band.
Reason :
Electrons do not obey Pauli's exclusion principle.

1 Both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.

2 Both Assertion and Reason are correct but Reason is not the correct explanation of the Assertion.

3 Assertion is correct but Reason is incorrect.

4 Assertion is incorrect but reason is correct.

Explanation:

Metals are solids (except $H g$ ). They have single energy band (for carriers viz. electrons) in the sense that valence band and conduction band overlop: The band formation is any solids is due to extension of Pauli exclusion principle which is originally for atoms
$\Rightarrow$ Reason is false. So correct option is (3).

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