Question

In a photo-electric effect experiment, photons of energy 5 eV are incident on a metal surface. They liberate photo-electrons which are just stopped by an electrode at a potential of -3.5 V with respect to the metal. The work function of the metal is :

• A. 1.5 eV
• B. 3.5 eV
• C. 5. 0 eV
• D. 8.5 eV

Answer 1

Answer: (A)

1.5 eV

Kinetic Energy lost due to stopping potential $=e\times 3.5$ V
$=3.5eV$
So,
From the question, the photoelectric equation becomes,

$5-W=3.5$

$\Rightarrow W=1.5$ eV

So, the answer is option (A).