The work function `(phi)` of some metals is listed can have principal quantum of metals which will show photoelectric effect when light of `300` nm wavelength falls on the metal is Metal `Li Na K Mg Cu Ag Fe Pt W phi(eV) 2.4 2.3 2.2 3.7 4.8 4.3 4.7 6.3 4.75 `

Answer

D

Explanation

Since the value of `hc = 1240 eV nm `
Energy coreresponding to `lambda = 300 nm`is
`- (1240 eV nm)/(100 nm) = 4.134 eV`
Electron having `phi lt 4.134 eV ` will show photoelectric effect, are Li ,Ni, K and` Mg rArr`
So number of means showing photo-electric will be four ,i.e. Li ,Ni, K and Mg