The effective density of states at the conduction band edge of Ge is 1.04 × 1019 cm-3 at room temperature (300 K). Ge has an optical band gap of 0.66 eV. The intrinsic carrier concentration (in cm-3) in Ge at room temperature (300 K) is approximately

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

The 2018 Nobel Prize in Physics has been awarded in laser physics for the optical tweezers and their applications to biological systems for the method of generating high-intensity, ultra-short optical pulses. Which of the following verifies the given statement? I: The 2018 Nobel Prize in Physics has been awarded in laser physics for the optical tweezers. II: The 2018 Nobel Prize in Physics has been awarded for applications of the optical tweezers to biological systems. III: The 2018 Nobel Prize in Physics has been awarded for the method of generating high-intensity, ultra-short optical pulses using the optical tweezers.

A

Only I

B

Only II and III

C

Only I and II

D

Only I and III

E

All of these

The conduction band edge in the p material is not at the same level to that of conduction band edge in the n material. Is it true or false?

A

True

B

False

Hotel Aditya has 10 single AC rooms, 5 double AC rooms and 18 non AC rooms. The fixed monthly rent of hotel is 150,000. The per day maintenance cost is Rs. 100 for double AC room, Rs. 75 for single AC room and Rs. 40 for non AC room. The per day charges are Rs. 600 for double AC room, Rs. 400 for single AC room and Rs. 250 for non AC room. In April 2003, the occupancy rate of non AC room was 50%, 70% of single AC room and 40% of double AC rooms. Find the profit/loss % for that particular month.

A

10.33% (profit)

B

10.33% (loss)

C

5.67% (loss)

D

5.67% (profit)

E

No profit, no loss

কোন এলাকার লিঙ্গ অনুপাত 104 দ্বারা বুঝায়- i. 100 জন মহিলা থাকলে 104 জন পুরুষ আছে ii. প্রতি একশজন নারীর জন্য 104 জন পুরুষ iii. 100 জন পুরুষ থাকলে 104 জন মহিলা আছে নিচের কোনটি সঠিক?

A

i ও ii

B

i ও iii

C

ii ও iii

D

i ii ও iii

The following question, there are three statements I, II and III. Read the question carefully and mark your answer according to which statements(s) is/are sufficient to the answer the question. Find the total cost of flooring a room? Statement I: The length of the room is 70% more than the breadth of the room Statement II: The cost of flooring some other room whose length is twice the length of the given room and breadth is one third of the breadth of the given room is Rs.3000 less than the cost of flooring of given room Statement III: The perimeter of the room is 90 m and cost of flooring is Rs. 20 per m2

A

I and III

B

I and III or II

C

I and II

D

Only III

E

None of these

An object X sinks in liquids P and Q but floats in liquid R. Which of the following conclusions can be made from these observations? A) Density of X is more than the density of P B) Density of X is less than the density of R C) Density of P is equal to the density of R D) Density of P is less than the density of R

A

A, B, C

B

A, B, D

C

B, C, D

D

A, C, D

A GSM cellular telephone standard requires a minimum of 9 dB rejection of interfering signal levels of -23 dBm at 3 MHz from the carrier, -33 dBm at 1.6 MHz from the carrier, and -43 dBm at 0.6 MHz from the carrier, for a carrier level of -99 dBm. Determine the required local oscillator phase noise at 3 MHz carrier frequency offset.

A

-138 dBc/Hz

B

-128 dBc/Hz

C

-118 dBc/Hz

D

None of the mentioned

Which of the following equations represent the correct expression for the band diagram of the p-n junction? (E1=difference between the fermi level of material and conduction band of n material and E2=difference between the conduction band of n material and fermi level of n material)

A

Ecn – E f = (1/2)*EG – E1

B

Ecn – E f = (1/2)*EG – E2

C

Ef – Ecp = (1/2)*EG – E1

D

Ecn – Ef = (1/2)*EG + E1

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

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

The effective density of states at the conduction band edge of Ge is 1.04 × 10¹⁹ cm^-3 at room temperature (300 K). Ge has an optical band gap of 0.66 eV. The intrinsic carrier concentration (in cm^-3) in Ge at room temperature (300 K) is approximately

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