Question

In Photoelectric setup as soon as the potential reaches $V_o$ (stopping potential), the electrons stop coming out of the emitter plate.

• A. True
• B. False

Answer 1

The correct option is B

False

At high Potential if 10 electrons were coming out from the emitter then 10 were being received by the collector.

Now if you started reducing the potential to below 0 , the collector plate will start repelling the electrons or in other words the emitter will start attracting the electrons. In this process a few slow moving , poor electrons with less kinetic energy will not be able to reach to collector and in midway get pulled back in the emitter. Thereby reducing the current.

Now if I start reducing the potential further more and more electrons will start returning midway, back to the emitter plate. So what technically is happening is, that these electrons had some kinetic energy which wasn't sufficient enough to overcome the potential difference.

Now if you reduce the potential even further, even the electron with highest kinetic energy cannot overcome the potential difference and just before entering the collector plate loses all kinetic energy and is pulled back. This is when the photo current stops. And this potential is called the stopping potential.

So even at stopping potential electrons are coming out but they are not able to reach the collector plate.