Two metals X and Y have work functions 2eV and 5eV respectively. Which metal will emit electrons when it is irradiated with light of wavelenth 400 nm and why?

Explanation

Wavelength of incident light =`lambda = 400 nm lambda = 400 xx 10^(-9) m = 4 xx 10^(-7) m `
Energy of incident radiation = `E = (hc)/(lambda)`
`= (6.62 xx 10^(-34) xx 3 xx 10^8)/(4 xx 10^(-7))`
`= (19.86)/(4) xx 10^(-34 + 8 + 7)`
`= (4.965 xx 10^(-19))/(1.6 xx 10^(-19)) eV`
`E = 3.1 eV`
This energy is more than work function of ion metal X.` therefore` Metal X will emit electrons.