A emtal has threshold waveelngth of `6,000 overset @A`.Calculate
threshold frequecy

Explanation

Threshold wavelength = `lambda_0 = 6400 Å`
`lambda_0 = 6400 xx 10^(-10) m = 6.4 xx 10^(-7) m`
(i) Threshold frequency = `v_0 = c/(lambda_0)`
`v_0 = (3 xx 10^8)/(6.4 xx 10^(-7)) = 0.469 xx 10^(15)`
`v_0 = 4.69 xx 10^(14)Hz`
(ii) Work function = `phi_0 = hv_0 `
`phi_0 = 6.62 xx 10^(-34) xx 4.69 xx 10^14`
`= 31.05 xx 10^(-34 +14)`
`phi_0 = 3.105 xx 10^(-19)J`
`phi_0 = (3.105 xx 10^(-19))/(1.6 xx 10^(-19)) eV = 1.94 eV`
`phi_0 = 1.94 eV`.