Question

The radiation corresponding to 3 $\to$ s 2 transition of hydrogen atom falls on a metal surface to produce photoelectrons. These electrons are made to enter a magnetic field of $3\times {10}^{-4}T$ . If the radius of the largest circular path followed by these electrons is 100 mm, the work function of the metal is close to

• A. 3.8 eV
• B. 1.1 eV
• C. 1.8 eV
• D. 1.6 eV

Answer 1

The correct option is B 1.1 eV

$mv=qBR$

$K{E}_{max}=\frac{\left(m{v}^2\right)}{2m}=0.8eV$

$hv=13.6\left[\frac{1}{4}-\frac{1}{6}\right]$

$\therefore W=hv-K{E}_{max}$

$=13.6\times \frac{5}{36}-0.8=1.1eV$

Hence,

option $\left(B\right)$ is correct answer.