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Q. No.The band gap between the valence band and the conduction band in a certain material is \(3~\text{eV}.\) What is the longest wavelength of light that can create an electron-hole pair in the material, with the electron in the conduction band and the hole in the valence band?
(take \(hc=1240~\text{eV-nm}\) )
1. \(414~\text{nm}\)
2. \(300~\text{nm}\)
3. \(830~\text{nm}\)
4. \(207~\text{nm}\)
(take \(hc=1240~\text{eV-nm}\) )
1. \(414~\text{nm}\)
2. \(300~\text{nm}\)
3. \(830~\text{nm}\)
4. \(207~\text{nm}\)
Subtopic: Â Energy Band theory |
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The energy band gap of semiconducting material to produce violet (wavelength \(=4000~\mathring{A}\)) LED is (nearly):
1. \(3~\text{eV}\)
2. \(5~\text{eV}\)
3. \(1~\text{eV}\)
4. \(7~\text{eV}\)
1. \(3~\text{eV}\)
2. \(5~\text{eV}\)
3. \(1~\text{eV}\)
4. \(7~\text{eV}\)
Subtopic: Â Energy Band theory |
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When semiconductor is heated, its resistance:
| 1. | decreases |
| 2. | increases |
| 3. | remains the same |
| 4. | may increase or decrease depending on the semiconductor |
Subtopic: Â Energy Band theory |
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Specify which of the following type of material might satisfy these descriptions:
A half-filled valence band, an empty conduction band, and an energy gap of \(1\) eV.
A half-filled valence band, an empty conduction band, and an energy gap of \(1\) eV.
| 1. | conductor |
| 2. | insulator |
| 3. | semiconductor |
| 4. | none of the above |
Subtopic: Â Energy Band theory |
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In a good conductor, the energy gap between the conduction band and the valence band is:
1. Infinite
2. Wide
3. Narrow
4. Zero
Subtopic: Â Energy Band theory |
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Identify the incorrect statement from the following:
| 1. | The resistivity of a semiconductor increases with an increase in temperature. |
| 2. | Substances with an energy gap of the order of \(10~\text{eV}\) are insulators. |
| 3. | In conductors, the valence and conduction bands may overlap. |
| 4. | The conductivity of a semiconductor increases with an increase in temperature. |
Subtopic: Â Energy Band theory |
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AIPMT - 2005
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In the energy band diagram of a material shown below, the open circles and filled circles denote holes and electrons respectively. The material is a/an:
| 1. | \(\mathrm{p}\text-\)type semiconductor |
| 2. | insulator |
| 3. | metal |
| 4. | \(\mathrm{n}\text-\)type semiconductor |
Subtopic: Â Energy Band theory |
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AIPMT - 2007
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A semiconductor has a negative temperature coefficient of:
| 1. | resistance |
| 2. | conductance |
| 3. | both resistance and conductance |
| 4. | neither resistance nor conductance |
Subtopic: Â Energy Band theory |
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Carbon, Silicon, and Germanium atoms have four valence electrons each. Their valence and conduction bands are separated by energy gaps represented by \(\left(E_g\right)_C,(E_g)_{Si}~\text{and}~(E_g)_{Ge}\) respectively. Which one of the following relationships is true in their case?
| 1. | \(\left(E_g\right)_C<\left(E_g\right)_{G e} \) | 2. | \(\left(E_g\right)_C>\left(E_g\right)_{S i} \) |
| 3. | \(\left(E_g\right)_C=\left(E_g\right)_{S i} \) | 4. | \(\left(E_g\right)_C<\left(E_g\right)_{S i}\) |
Subtopic: Â Energy Band theory |
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As the temperature increases, the electrical resistance:
| 1. | decreases for conductors but increases for semiconductors. |
| 2. | increases for both conductors and semiconductors. |
| 3. | decreases for both conductors and semiconductors. |
| 4. | increases for conductors but decreases for semiconductors. |
Subtopic: Â Energy Band theory |
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NEET - 2022
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