Work function of lithium and copper are respectively 2.3 eV and 4.0 eV. Which one of the metal will be useful for the photoelectric cell working with visible light? (h=`6.6xx10^(-34)`J-s, c=`3xx10^(8)`m/s

Options

A. Lithium
B. Copper
C. Both
D. None of these

Answer

A

Explanation

`lamda_0(Å)=(12375)/(phi_0(eV))`
`(lamda_0)_(Li)=(12375)/(2.3)=5380Å, (lamda_0)_(cu)=( 12375)/4=3094Å`
`3094Å` does not lie in visible region, but it lie in UV region.
Hence, Lithium will be considered.