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A photodiode is an optoelectronic device in which current carriers are generated by photons through photo $-$ excitation i.e., photo conduction by light. It is a $p-n$ junction fabricated from a photosensitive semiconductor and provided with a transparent window so as allow light to fall on its function. A photodiode can turn its current $ON$ and $\text{OFF}$ in nanoseconds. So, it can be used as a fastest photo $-$ detector.

1. A $p-n$ photodiode is fabricated from a semiconductor with a band gap of $2.5\ eV$. It can detect a signal of wavelength:

1. $4000\ nm.$
2. $6000\ nm.$
3. $4000Â.$
4. $6000Â.$

2. Three photo diodes $D_1 ,D_2$ and $D_3$ are made of semiconductors having band gap of $2.5\ eV, 2\ eV,$ and $3 \ eV ,$ respectively. Which one will be able to detect light of wavelength $6000Â$?

1. $D_1$
2. $D_2$
3. $D_3$
4. $D_1$ and $D_2$ both.

3. Photodiode is a device:

1. Which is always operated in reverse bias.
2. Which of always operated in forward bias.
3. In which photo current is independent of intensity of incident radiation.
4. Which may be operated in forward or reverse bias.

4. To detect light of wavelength $500\ nm,$ the photodiode must be fabricated from a semiconductor of minimum bandwidth of:

1. $1.24\ eV$
2. $0.62\ eV$
3. $2.48\ eV$
4. $3.2eV$

5. Photodiode can be used as a photodetector to detect :

1. Optical signals.
2. Electrical signals.
3. Both $(a)$ and $(b)$.
4. None of these.