Question

The work function of a metal is 2.5 eV. When photon of some proper energy is made incident on it, then an electron of 1.5 eV is emitted. The energy of photon will be

• A. $4eV$
• B. $1eV$
• C. $1.5eV$
• D. $2.5eV$

Answer 1

The correct option is A $4eV$

The energy of photoelectron emitted out is
$E=h\nu -\varphi$
where, $h\nu$ is the energy of incident photon, $\varphi$ is the photoelectric work function of the metal.
$h\nu =E+\varphi$
$h\nu =1.5+2.5$
$h\nu =4eV$
Hence, the energy of photon will be 4eV.

So, the answer is option (A).