Question

Electrons are emitted with zero velocity from a metal surface when it is exposed to radiation of wavelength ` 6800` Å . Calculate threshold frequency `( v_0)` and work function `(W_0)` of the metal.

Answer 1

`E// "photon" = (hc)/(lambda) = ( 6.626 xx 10^(-34) xx 3.0 xx 10^8)/( 6800 xx 10^(-28)` .
`= 2. 92 xx 10^(19) J`
`E//" photon" = 2.92 xx 10^(-19) J` = work function
(The ejection has zero velocity )
Threshold frequency `= c/(lambda) = ( 3 xx 10^8)/( 6800 xx 10^(-10))`
` = 4. 41 xx 10^(14) sec ^(-1)`.