Question

The work functions for metals $\text{A, B}$ and $\text{C}$ are respectively $1.92\text{eV},2.0\text{eV}$ and $5\text{eV}.$ The metals which will emit photo-electrons for a radiation of wavelength $4100\mathring{\text{A}}$ is/are
[Take $hc=12400\text{(eV)}\mathring{\text{A}}$ ]

• A. $\text{A, C}$ only
• B. $\text{A}$ only
• C. $\text{A, B}$ only
• D. All the three metals

Answer 1

The correct option is C $\text{A, B}$ only

Work function for wavelength of $4100\mathring{\text{A}}$ is,

$W=\frac{hc}{\lambda }=\frac{12400}{4100}=3\text{eV}$

Now, we have

$\because W_A=1.92\text{eV},W_B=2.0\text{eV},W_C=5\text{eV}$

$\Rightarrow W_A\&W_B<W$ and $W_C>W$

Hence, $\text{A}$ and $\text{B}$ will emit photoelectrons.

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> Hence, $\left(C\right)$ is the correct answer.