Question

The kinetic energy of photoelectron emitted from the surface of a metal is \(7.2\times10^{-20}\,\text{J}\), when the metal is made to strike with light having wavelength \(\lambda\) nm. What is the value of \(\lambda\)? \[ (\text{Work function of metal}=4.5\,\text{eV};\; h=6.6\times10^{-34}\,\text{J s};\; c=3\times10^8\,\text{m s}^{-1};\; 1\,\text{eV}=1.6\times10^{-19}\,\text{J}) \]

• A. \(125\)
• B. \(250\)
• C. \(175\)
• D. \(150\)

Hint:

Use Einstein's photoelectric equation \[ \boxed{ \frac{hc}{\lambda}=\phi+K.E. } \] Always convert the work function from eV to joules before substituting.

Answer 1

The Correct Option is B