The work function for a metal is 4 ,eV. To emit a photo electron … - Vidyadip

MCQ

The work function for a metal is $4 \,eV.$ To emit a photo electron of zero velocity from the surface of the metal, the wavelength of incident light should be : ................ $\mathop {\rm{A}}\limits^{\rm{o}} $

A
$2700$
B
$1700$
C
$5900$
✓
$3100$

✓

Answer

Correct option: D.

$3100$

d
$h v=h v_{0}+K E$ for zero velocity $K E=0$

$h v=h v_{0}$

$h v=4 e V$

$\frac{h c}{\lambda}=4 e V$

$\lambda=\frac{h \times c}{4 e V}$

$=\frac{6.626 \times 10^{-34} \times 3 \times 10^{8}}{4 \times 1.6 \times 10^{-19}}=3100 \mathrm{A}^{\circ}$

Hence, the correct option is $D$

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