A : There is almost no time-lag between the incidence of light and the emission of photoelectrons .
R : A photon transfer almost all its energy to a single electron in a metal .

Options

A. If both Assertion & Reason are ture and the reason is the correct explanation of the assertion , then mark (1) .
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion , then mark (2) .
C. If Assertion is true statement but Reason is false , then mark (3)
D. If both Assertion and Reason are false statements , then mark (4) .

Answer

To solve the assertion and reason-based question, we will analyze both statements step by step.

### Step 1: Understand the Assertion
**Assertion (A)**: "There is almost no time-lag between the incidence of light and the emission of photoelectrons."

- The photoelectric effect describes the phenomenon where light (or photons) strikes a metal surface and causes the emission of electrons (photoelectrons).
- In this process, when light of sufficient frequency hits the metal surface, it can instantaneously transfer energy to the electrons.
- The lack of a time-lag indicates that the interaction between the light and the electrons happens almost instantaneously, supporting the particle nature of light.

### Step 2: Understand the Reason
**Reason (R)**: "A photon transfers almost all its energy to a single electron in a metal."

- According to Einstein's photoelectric equation, the energy of a photon is given by \(E = h\nu\), where \(h\) is Planck's constant and \(\nu\) is the frequency of the light.
- For an electron to be emitted from the metal, it must overcome the work function (\(\phi\)) of the metal. The excess energy after overcoming the work function is converted into the kinetic energy of the emitted electron.
- This means that a photon can indeed transfer almost all its energy to a single electron, provided the energy of the photon is greater than the work function.

### Step 3: Analyze the Relationship Between A and R
- Both statements are correct. The assertion accurately describes the instantaneous nature of the photoelectric effect, while the reason explains the mechanism behind it.
- The reason provides a valid explanation for the assertion since the rapid emission of photoelectrons is due to the efficient energy transfer from photons to electrons.

### Conclusion
Both the assertion and the reason are correct, and the reason is the correct explanation for the assertion.

### Final Answer
Both A and R are correct, and R is the correct explanation of A.

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