Energy Band Theory

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. p-type semiconductor

2. insulator

3. metal

4. n-type semiconductor

A p-n photodiode is made of a material with a bandgap of 2.0 eV. The minimum frequency of the radiation that can be absorbed by the material is nearly:

1. $10\backslash times{10}^{14}$ $\mathrm{Hz}$

2. $5\backslash times{10}^{14}$ $\mathrm{Hz}$

3. $1\backslash times{10}^{14}$ $\mathrm{Hz}$

4. $20\backslash times{10}^{14}$ $\mathrm{Hz}$

A photodiode is fabricated from a semiconductor with a band gap of It can detect a signal of wavelength:
1.
2.
3.
4.

and both have the same lattice structure, having bonding electrons in each. However, is an insulator whereas is an intrinsic semiconductor. This is because:

1.	in the case of the valence band is not completely filled at absolute zero temperature.
2.	in the case of the conduction band is partly filled even at absolute zero temperature.
3.	the four bonding electrons in the case of lie in the second orbit, whereas in the case of they lie in the third.
4.	the four bonding electrons in the case of lie in the third orbit, whereas for they lie in the fourth orbit.

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.