Answer:
E = 401.3 eV
Explanation:
As we know that the thinnest gap in the direction of metal is given as
[tex]t = 3.09 nm[/tex]
so here we can say that lowest energy of photon will not able to break this electron from above thickness
so we will have
[tex]E = \frac{hc}{\lambda}[/tex]
here we have
[tex]hc = 1240 nm-eV}[/tex]
also we have
[tex]\lambda = 3.09 nm[/tex]
so we will have
[tex]E = \frac{1240}{3.09} eV[/tex]
[tex]E = 401.3 eV[/tex]