Tag: energy bands

Questions Related to energy bands

The forbidden gap for a pure silicon at the room temperature is _______eV.

physics semiconductors band theory of solids, a brief introduction electron energies in solids energy bands

  1. Less than one

  2. 1.1

  3. 3

  4. 9

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Correct Option: B
Explanation:

The forbidden gap for a pure Si at room temperature is 1.1 eV.

A pure germanium crystal at absolute zero is:

physics semiconductors band theory of solids, a brief introduction electron energies in solids energy bands

  1. An insulator.

  2. A good conductor.

  3. A semiconductor.

  4. None of the above.

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Correct Option: A
Explanation:

At absolute zero, a semiconductor is an insulator.

State whether True or False :

A semiconductor at absolute zero become a insulator.

physics semiconductors band theory of solids, a brief introduction electron energies in solids energy bands

  1. True

  2. False

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Correct Option: A
Explanation:

The conductivity and non-conductivity of material are dependent on the motion of electrons. If the motion is happening it is conductor.

Now, at absolute zero, the temperature is so low that it stops the motion of the electrons. Thus making it a complete insulator.
$\Rightarrow$  Statement (A) is the correct answer.

What is forbidden energy gap(Eg) or band gap?

physics semiconductors band theory of solids, a brief introduction electron energies in solids energy bands

  1. Forbidden energy gap ${ E } _{ g }$ is the difference of energy levels of conduction band and within conduction band

  2. Forbidden energy gap ${ E } _{ g }$ is the difference of energy levels of conduction band and valence band.

  3. when there is no energy

  4. conduction band

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Correct Option: B
Explanation:

Forbidden energy gap ${ E } _{ g }$ is the difference of energy levels of conduction band and valence band.

Give band gap Eg value for conductor, insulator and semiconductor?

physics semiconductors band theory of solids, a brief introduction electron energies in solids energy bands

  1. Conductor$<1MeV$, insulation $\ge 6eV$, semiconductor $\approx 8eV$.

  2. Conductor$<1MeV$, insulation $\ge 6eV$, semiconductor $\approx 1eV$.

  3. Conductor$<2MeV$, insulation $\ge 6eV$, semiconductor $\approx 1eV$.

  4. Conductor$<1MeV$, insulation $\ge 7eV$, semiconductor $\approx 1eV$.

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Correct Option: B
Explanation:

Conductor$<1MeV$, insulation $\ge 6eV$, semiconductor $\approx 1eV$.

The electrical conductivity of a semiconductor increases when electromagnetic radiation of wavelength shorter than $2480nm$ is incident on it The forbidden band gap for the semiconductor is 

physics semiconductors band theory of solids, a brief introduction electron energies in solids energy bands

  1. $0.9eV$

  2. $0.7eV$

  3. $0.5eV$

  4. $1.1eV$

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Correct Option: C

In germanium crystal, the forbidden energy gap in joule is:

physics semiconductors band theory of solids, a brief introduction electron energies in solids energy bands

  1. $1.6\times 10^{-19}$

  2. zero

  3. $1.12\times 10^{-19}$

  4. $1.76\times 10^{-19}$

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Correct Option: C

The energy of radiation emitted by $LED$ is :

physics semiconductors band theory of solids, a brief introduction electron energies in solids energy bands

  1. greater than the band gap of the semiconductor used

  2. always less than the band gap of the semiconductor used.

  3. always equal to the band gap of the semiconductor used.

  4. equal to the or less than the band gap of the semiconductor used

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Correct Option: D

Given that the mobility of electrons in Ge is $0.4$ metre square/volt sec and electronic charge is $ 1.6 \times 10^{-19}$C. How many door atom (per $ m^3$) have in semiconductor of conductivity $500$ mho/m:-

physics semiconductors band theory of solids, a brief introduction electron energies in solids energy bands

  1. $ 8 \times 10^{21}$

  2. $8 \times 10^{15}$

  3. $5 \times 10^{21}$

  4. $8 \times 10^6$

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Correct Option: C

Three semiconductors are arranged in the increasing order of their energy gap as follows: the correct arrangement is

physics semiconductors band theory of solids, a brief introduction electron energies in solids energy bands

  1. Tellurium, germanium, silicon

  2. Tellurium,silicon , germanium

  3. silicon, germanium, Tellurium

  4. silicon, Tellurium, germanium

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Correct Option: A