Physics 102 question

A metal having a work function of 1.2 eV has light whose photon energy is 3.6 eV shining on it. What is maximum possible kinetic energy of the electrons that are ejected?

A.5.4 × 10-19 J

B.3.8 x 10-19 J

C.4.9 × 10-19 J

D.5.8 x 10-19 J J

E.4.4 × 10-19 J

 

It takes 1.2 eV to eject the electron, so of the 3.6 eV energy from the photon $3.6eV -1.2eV = 2.4 eV$ will go into the kinetic energy of the ejected electron. Next we convert from eV to Joules: $1 eV = 1.6022x10^{-19} J$, so the ejected electron will have kinetic energy

 

$KE = 2.4 eV = 3.8 \times10^{-19} J.$

 

Choose answer B.