Скачать или смотреть Assertion A ; Emission of electrons in photoelectric effect can be suppressed by applying a sufficie

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : Emission of electrons in photoelectric effect can be suppressed by applying a sufficiently negative electron potential to the
photo emissive substance.
Reason (R) : A negative electric potential, which stops the emission of electrons from the surface of a photo emissive substance, varies linearly with frequency of incident radiation.
In the light of the above statements, choose the most appropriate answer from the options given below:
(1) (A) is false but (R) is true.
(2) (A) is true but (R) is false.
(3) Both (A) and (R) are true and (R) is the correct explanation of (A).
(4) Both (A) and (R) are true but (R) is not the correct explanation of (A).

🎥 Video Title: Photoelectric Effect | JEE Mains 2025 PYQ Solved 🔥 | Assertion & Reason
📚 Chapter/Topic: Modern Physics | Photoelectric Effect
🎯 Exam Focus: JEE Mains 2025 | NEET 2025

📖 In This Video:
In this video, I’ve solved a JEE Mains 2025 Previous Year Question (PYQ) based on the photoelectric effect. The problem involves analyzing two statements: an Assertion (A) and a Reason (R), and determining their validity and relationship. This problem is a perfect blend of theory and application, making it a must-watch for all JEE and NEET aspirants. I’ve explained the entire concept in a simple and engaging way, focusing on the theory and avoiding complex calculations.

🔥 Key Highlights:
✅ Understanding the photoelectric effect and how it works.
✅ How a negative potential can suppress the emission of photoelectrons.
✅ Analyzing the relationship between the stopping potential and the frequency of incident radiation.
✅ Step-by-step breakdown of the problem without complex formulas.
✅ Tips to approach similar questions in JEE Mains 2025.

Key Concepts:

Photoelectric Effect:

When light of sufficient frequency (above the threshold frequency) strikes a metal surface, electrons are emitted.

This phenomenon is known as the photoelectric effect.

Stopping Potential:

A negative potential applied to the metal surface can stop the emitted electrons from reaching the collector.

The minimum potential required to stop the most energetic electrons is called the stopping potential (V₀).

Relationship Between Stopping Potential and Frequency:

The stopping potential is related to the frequency of the incident radiation by the equation:
eV₀ = hν - φ,
where e is the charge of an electron, h is Planck's constant, ν is the frequency of the incident radiation, and φ is the work function of the metal.

This equation shows that the stopping potential V₀ varies linearly with the frequency ν of the incident radiation.

Connecting the Dots:

Assertion (A) states that applying a sufficiently negative potential can suppress electron emission. This is true because a negative potential creates an electric field that opposes the motion of the emitted electrons, eventually stopping them.

Reason (R) states that the stopping potential varies linearly with the frequency of the incident radiation. This is also true and is a direct consequence of the photoelectric equation.

However, Reason (R) does not explain Assertion (A). While both statements are true, the linear relationship between stopping potential and frequency is a separate observation and does not directly explain why a negative potential suppresses electron emission.

Final Answer:
Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A). Therefore, the correct option is:
(4) Both (A) and (R) are true but (R) is not the correct explanation of (A).

Why This Problem is Important:
This problem tests your understanding of the photoelectric effect, stopping potential, and their relationship with frequency, which are crucial topics for JEE Mains and NEET. By solving this problem, you’ll learn how to handle questions that involve analyzing relationships between statements, a common trend in competitive exams.

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