(a) distinguish between metals inlsulators and simi conductors on the baisi of their energy bands
(b) why are photodiodes used preferabley in reverse bias condlition can it detect a wavelength of 6000 nm justify

Explanation

`(b) lambda = 600 nm = 600 xx 10^(-9) m`
`E= (hc)/( lambda) = (6.63 xx 10^(34) xx 3 xx 10^(8))/(6000 xx 10^(-6))`
this is less than the band d gap therefore photodiode cannot detect it