The correct option is D 2.18×10−5 m
Since, the acceptor level is 57 meV above the valence band, at least 57 meV is needed to create a hole.
Let the λ be the wavelength of light, then photon will have energy, E=hcλ
So, to create a hole, hcλ≥57 meV
⇒λ≤hc57 meV
We know,
h=6.626×10−34 Js
c=3×108 ms−1
1 eV=1.6×10−19 J
⇒λ≤6.626×10−34×3×10857×10−3×1.6×10−19
⇒λ≤2.179×10−5 m≈2.18×10−5 m
⇒λmax=2.18×10−5 m
Hence, option (D) is correct.