Question

Three photo diodes D₁, D₂ and D₃ are made of semiconductors having band gaps of 2.5 eV, 2 eV and 3 eV, respectively. Which 0 ones will be able to detect light of wavelength 6000 Å?

Answer 1

In Photodiodes, electron and hole pairs are created by the junction photoelectric effect. That is the covalent bonds are broken by the EM radiations absorbed by the electron in the V.B. These are used for detecting light signals.

According to the problem,

The wavelength of light λ = 6000 Å = 6000 × 10^-10 m

The energy of the light photon `E = (hc)/λ = (6.6 xx 10^-34 xx 3 xx 10^8)/(6000 xx 10^-10 xx 1.6 xx 10^-19)` eV = 2.06 eV

The incident radiation is detected by the photodiode D₂ because the energy of incident radiation is greater than the band gap.