A photon of wavelength `4 xx 10 ^(-7) m` strickes on metal surface, the work function of the metal being `2.13` eV. Calculate
the velocity of the photoelectron `(1 eV = 1. 6020 xx 10 ^(-19) J)`

Explanation

We are given that
Wavelength of phton ` 4 xx 10 ^(-7) m`
Work function of metal `= 2.13 eV`
we know that `K. E. = (1)/(2) mv ^(2) `
or, `v = sqrt (( 2 K. E. )/( m )) = sqrt (( 2 xx 0. 9 7 xx 1. 6 xx 10 ^(-19) J )/( 9.1 xx 10 ^(-31) kg ))`
`= sqrt (( 0. 97 xx 3.2 xx 10 ^(12) kgms ^(-1))/( 9.1 kg ) ) = 5.84 xx 10^(5) ms ^(-1) [ because J = kg ms ^(-1) ]`
`therefore ` Velocity of the photoelectron is `5. 84 xx 10 ^(5) ms ^(-1).`