Question

The radiation corresponding to 3 $\to$ 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 $10.0mm$, the work function of the metal is close to

• A. $0.8eV$
• B. $1.6eV$
• C. $1.8eV$
• D. $1.1eV$

Answer 1

Answer: (D)

$1.1eV$

$mv=qBR$

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

$hv=13.6[\frac{1}{4}-\frac{1}{9}]$

$\therefore W=hv-K{E}_{\left(max\right)}$$=13.6\times \frac{5}{36}-0.8=1.1eV$ .