Question

Light of wavelength $3500A^0$ is incident on two metals $1$ and $2$ whose work function are $4.5eV$ and $2.5eV$ respectively then:

• A. both $1$ and $2$ emit photoelectrons
• B. Only $2$ emit photoelectrons
• C. Only $1$ emit photoelectrons
• D. neither $1$ nor $2$ emit photoelectrons

Answer 1

The correct option is B Only $2$ emit photoelectrons

Given that,

Wave length$\lambda =3500\stackrel{\circ }{A}$

Work function of metal $1=4.5eV$

Work function of metal $2=2.5eV$

We know that,

$E=\frac{hc}{\lambda }$

$E=\frac{12375}{3500}$

$E=3.5eV$

So, only $2$ metal having work function less than $3.5eV$ can emit photoelectrons for the incident radiation of wavelength $3500\AA$