The band structure in an n-type semiconductor is<br><img src="/images/question-image/engineering-chemistry/chemical-bonding-and-molecular-structure/1689828997-the-band-structure-in-an-n-type-semiconductor.png" title="Chemical Bonding and Molecular Structure mcq question image" alt="Chemical Bonding and Molecular Structure mcq question image">

An N-type semiconductor having uniform doping is biased as shown in the figure. If EC is the lowest energy level of the conduction band, EV is the highest energy level of the valance band and EF is the Fermi level, which one of the following represents the energy band diagram for the biased N-type semiconductor?

A

B

C

D

In a diatomic molecule, the inter-nuclear separation of the ground and first excited electronic state are the same as shown in the figure. If the molecule is initially in the lowest vibrational state of the ground state, then the absorption spectrum will appear as
Atomic and Molecular Physics mcq question image

Atomic and Molecular Physics mcq question image

A

B

C

D

Five energy levels of a system including the ground state are shown below. Their lifetimes and the allowed electric dipole transitions are also marked.
Atomic and Molecular Physics mcq question image

Which one of the following transitions is the most suitable for a Continuous Wave (CW) laser?

A

1 → 0

B

2 → 0

C

4 → 2

D

4 → 3

A simplified energy band-diagram of an intrinsic semiconductor at thermal equilibrium (300 K) is shown. In the accompanying table, which one of the four cloumns correctly represents the listed parameters? Assume same effective mass for electrons and holes.
Physics of Metals in Metallurgy mcq question image

Physics of Metals in Metallurgy mcq question image

A

Parameter	Energy-difference
Parameter	Column 1	Column 2	Column 3	Column 4
Band-gap	ΔE₂	ΔE₁	ΔE₂	ΔE₁
Electron affinity	$$\frac{{\Delta {E_1}}}{2}$$	ΔE₂ - ΔE₁	$$\frac{{\Delta {E_2}}}{2}$$	ΔE₂ - $$\left( {\frac{{\Delta {E_1}}}{2}} \right)$$
Work function	ΔE₁ + ΔE₂	ΔE₂ - $$\left( {\frac{{\Delta {E_1}}}{2}} \right)$$	ΔE₁ - $$\frac{{\Delta {E_2}}}{2}$$	ΔE₂ + $$\left( {\frac{{\Delta {E_1}}}{2}} \right)$$

Column 1

B

Column 2

C

Column 3

D

Column 4

An intrinsic semiconductor with mass of a hole m_h, and mass of an electron m_e is at a finite temperature T. If the top of the valence band energy is E_v and the bottom of the conduction band energy is E_c, the Fermi energy of the semiconductor is

A

$${E_F} = \left( {\frac{{{E_v} + {E_c}}}{2}} \right) - \frac{3}{4}{k_B}T\ln \left( {\frac{{{m_h}}}{{{m_e}}}} \right)$$

B

$${E_F} = \left( {\frac{{{k_B}T}}{2}} \right) + \frac{3}{4}\left( {{E_v} + {E_c}} \right)\ln \left( {\frac{{{m_h}}}{{{m_e}}}} \right)$$

C

$${E_F} = \left( {\frac{{{E_v} + {E_c}}}{2}} \right) + \frac{3}{4}{k_B}T\ln \left( {\frac{{{m_h}}}{{{m_e}}}} \right)$$

D

$${E_F} = \left( {\frac{{{k_B}T}}{2}} \right) - \frac{3}{4}\left( {{E_v} + {E_c}} \right)\ln \left( {\frac{{{m_h}}}{{{m_e}}}} \right)$$

Take NA as the number of Anti-bonding molecular orbitals and NB as the number of Bonding molecular orbitals. The molecule is stable when NA ____________ NB.

A

is greater than

B

is equal to

C

is less than

D

is greater than or equal to

Which of the following statements is/are correct? 1) Conductor contains a large number of electrons in the conduction band at room temperature. No energy gaps exist and the valence and conduction bands overlap. 2) A semiconductor is a material in which the energy gap is so large that practically no electron can be given enough energy to jump this gap. 3) An insulator is a solid with an energy gap small enough for electrons to cross rather easily from the valence band to conduction band.

A

1 only

B

2 only

C

3 only

D

1, 2 and 3

Three molecular ionic states, P-R are possible for the amino acid histidine. Identify the correct choice of pH values, respectively for the observation of the ionic states P-R.
Basics of Organic Reaction Mechanism mcq question image

Basics of Organic Reaction Mechanism mcq question image

A

P at pH 1; Q at pH 12; R at pH 7

B

P at pH 7; Q at pH 1; R at pH 12

C

P at pH 12; Q at pH 7; R at pH 1

D

P at pH 12; Q at pH 1; R at pH 7

Which of the following statements are correct? 1. A lowpass filter passes low frequencies and stops high frequencies. 2. A highpass filter passes high frequencies and rejects low frequencies 3. A bandpass filter passes frequencies within a frequency band and attenuates frequencies outside the band. 4. A bandstop filter passes frequencies within the band and blocks/attenuates frequencies outside a frequency band.

A

1, 2 and 4 only

B

1, 3 and 4 only

C

2, 3 and 4 only

D

1, 2 and 3 only

Determine the resistance value and tolerance of a resistor that has the following color bands; first band is red, second band is red, third band is orange, and the fourth band is gold

A

220 Ohm, 5%

B

220 Ohm, 10%

C

22,000 Ohm, 5%

D

22, 000 Ohm, 10%

E

None of the above

The band structure in an n-type semiconductor is

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