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Electronic Devices and Circuits - Engineering

Q1:

An n type semiconductor is illuminated by a steady flux of photons with energy greater than the band gap energy. The change in conductivity Δσ obeys which relation?
[ Here, e is the electron charge, μn electron mobility, μp hole mobility, Δn (Δp) is the excess electron (hole) density ].

A Δσ = 0

B Δσ = e(σn + σp) Δn

C Δσ = e(μnΔn - μpΔp)

D Δσ = e μnΔn

ANS:B - Δσ = e(σn + σp) Δn

Yeah its D. Since mobility and e are both constants so, if there will be a change in conductivity it is probably due to change in concentration of carriers.