[填空题]
The energy gap between valence and conduction bands in germanium is 0.72 eV.oym5*ba8sq u8)iob7l zrdf /5 Wha5ylfzm8*s i8d7oa/ bro u)q5bkz x (o:r+,dr d1 d6*xrja++lm woxwm:t range of wavelengths can a photon have to excite an electron from the ,1 r+xrjd+mrwk *l+z( :dxw: om6dxaotop of the valence band into the conduction band? $\lambda \leq$ $ \ \mu\text{m}$
