Question

$K_{max}(\text{in}eV)=3,$ and frequency of light $(inHz)=1\times {\left(10\right)}^{15}$ for a metal used as a cathode in a photoelectric experiment. The threshold frequency of light for the photoelectric emission from the metal is -

• A. $1\times 10^{14}\text{ Hz}$
• B. $1.5\times 10^{14}\text{Hz}$
• C. $2.1\times 10^{14}\text{ Hz}$
• D. $2.7\times 10^{14}\text{Hz}$

Answer 1

Answer: (D)

Given, ${\text{K}}_{max}=3\text{eV}$
$h=4.125\times 10^{-15}\text{eV}{\text{Hz}}^{\text{-1}}$
$h\nu =K_{max}+W$
$4.125\times 10^{-15}\times 10^{15}=3+W$
or $4.125=3+W$
or $W=1.125$
The threshold frequency
${\nu }_0=\frac{W}{h}$
${\nu }_0=\frac{1.125}{4.125\times 10^{-15}}$
${\nu }_0=\frac{1.125\times 10^{-15}}{4.125}$
${\nu }_0=2.72\times 10^{14}$