Question

Light of wavelength $1800\stackrel{\circ }{A}$ ejects photoelectrons from plate of a metal whose work function is $2eV$. Electron ejected from the plate with maximum kinetic energy

• A. $4.88eV$
• B. $6.72eV$
• C. $1.43eV$
• D. $2.54eV$

Answer 1

Answer: (C)

$1.43eV$

Energy of incident light = $\frac{hc}{\lambda }$

$\lambda$ = 180 $\stackrel{{}_{\circ }}{A}$

we know that

hv = ${\varphi }_0+\frac{1}{2}\times m{v}^2$

$\frac{hc}{\lambda }={\varphi }_1+\frac{1}{2}\times m{v}^2$

$K.E_{max}=\frac{hc}{\lambda }-{\varphi }_0$

= $0.011\times {10}^{-16}-3.2\times {10}^{-19}J$

=$7.3\times {10}^{-19}J$

= 1.43 ev