When light of a certain frequency is incident on a metal surface, no photoelectrons are emitted. If the frequency of the light is increased, what happens to the stopping potential?

De sage

1 year ago

may God deliver me in situation of not knowing the answer but seeing the option with the longest sentence choose it as my answer 😫😂😂😂😂😫😫😫😫

Velapearl

2 months ago

Alright, let’s slow this down properly because this one looks scary at first, but it is actually one of the most predictable topics in Physics.
Let’s start from the very beginning, like you have never seen any of these words before.
The question says light of a certain frequency is shined on a metal surface and no photoelectrons are emitted. That simply means the light does not have enough energy to knock electrons out of the metal. So nothing is coming out at all. The metal is just “ignoring” the light because it is too weak in terms of frequency.
Now in photoelectric effect, frequency is the real “power source”, not intensity. That is a very important idea JAMB loves.
Frequency is what decides how energetic each photon is. Higher frequency means higher energy per photon. So when they say the frequency is increased, what they are really saying is that each tiny packet of light energy becomes stronger.
Now let’s connect this to stopping potential.
Stopping potential is the minimum voltage needed to stop the fastest emitted electrons from reaching the collector in a photoelectric tube. In simpler words, it is the “brake voltage” that stops electrons that have already been knocked out.
So here is the logic chain you should picture in your mind. First, light must be strong enough to eject electrons. Only after electrons are emitted do we even start talking about stopping potential.
In the first situation, nothing is emitted. That means the frequency was below the threshold frequency. Threshold frequency is the minimum frequency needed to even start the photoelectric effect. Below it, nothing happens at all.
Now when the frequency is increased, something important happens. You are now giving photons more energy. So once you cross the threshold, electrons will start to be emitted, and not just that, they will come out with more kinetic energy.
Now here is the key relationship that ties everything together. Stopping potential depends directly on the maximum kinetic energy of emitted electrons. If electrons come out faster and with more energy, you need a higher voltage to stop them.
So when frequency increases, photon energy increases, electron kinetic energy increases, and therefore stopping potential increases.
Now let’s carefully look at the options and clear the confusion.
Option A says the stopping potential does not change. That would only be true if frequency stayed the same. But here frequency is increasing, so energy is increasing. So this option is wrong.
Option B says stopping potential decreases. That would mean electrons are coming out with less energy when frequency increases, which contradicts the physics completely. So this is wrong.
Option C tries to confuse you by introducing intensity. Intensity is a distraction here. Intensity affects how many electrons are emitted, not their maximum energy. So this option is misleading and incorrect.
Option D says stopping potential increases. This matches the logic we just built. Higher frequency means higher photon energy, which means higher kinetic energy of electrons, which means higher stopping potential needed to stop them.
So the correct answer is D.
Now let me leave you with a simple mental picture that will save you in exams. Think of frequency as how hard light “hits” electrons. Low frequency is like weak knocks that cannot even open the door. Higher frequency is like stronger knocks that not only open the door but push things out faster. And stopping potential is just the electrical brake you use to stop those faster electrons.
If you remember that picture, you will stop guessing in these questions.