In photoelectric effect an em-wave is incident on a metal surface...

In photoelectric effect an em-wave is incident on a metal surface and electrons are ejected from the surface. If the work function of the metal is 2.14 eV and stopping potential is 2 V , what is the wavelength of the em-wave ? (Given hc

=1242 \mathrm{eVnm}

where h is the Planck's constant and c is the speed of light in vaccum.)

Options

A300 nm
B400 nm
C600 nm
D200 nm

Correct answer

A. 300 nm

Step-by-step solution

\begin{aligned} & \phi=2.14 \\ & V_S=2 \mathrm{~V} \end{aligned}

Using photoelectric equation.

\begin{aligned} & \frac{h c}{\lambda}=2.14+2=4.14 \mathrm{eV} \\ & \lambda=\frac{1242}{4.14}=300 \mathrm{~nm} \end{aligned}

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