A p-n junction is fabricated from a semiconductor with band gap of `3.0 eV`. Can it detect a wavelength of (i) `600nm` (ii)`400nm`?
Given, `h=6.6xx10^(-34)Js`.

Explanation

(i) Energy `E=(hc)/(lambda)`
`(6.6xx10^(-34)xx3xx10^(8))/(600xx10^(-9)xx1.6xx10^(-19))eV`
`=2.06 eV lt 3.0eV`
As `E lt E_(g)`, so p-n junction cannot detect the rediation of wavelength 600nm
(ii) `E=(6.6xx10^(-34)xx3xx10^(8))/(400xx10^(-9)xx1.6xx10^(-19))`
`=3.1 eV gt 3.0eV`
As` E gt E_(g)`, so p-n junction can detect the radiation of wavelength 400nm.