Calculate the work function of a metal in eV,if its threshold waveelngth is `6,800 overset A` and `h=6.62 xx 10^(-27) erg s`.

Explanation

Threshold wavelength = `lambda_0 = 6800 Å`
`lambda_0 = 6800 xx 10^(-10) m = 68 xx 10^(-8) m`
`h = 6.62 xx 10^(-27) `erg second
`h = 6.62 xx 10^(-34) Js `
Work function of metal = `lambda_0 = (hc)/(lambda_0)`
`phi_0 = (6.62 xx 10^(-34) xx 3 xx 10^8)/(68 xx 10^(-8))`
`= (19.86)/(68) xx 10^(-34 + 8 + 8)`
`= 0.29 xx 10^(-18) J = 2.9 xx 10^(-9) J`
`phi_0 (2.9 xx 10^(-19))/(1.6 xx 10^(-19)) eV = 1.81 eV`