Threshold wavelength of certain metal is `lamda_0` A radiation of wavelength `lamdaltlamda_0` is incident on the plate. Then, choose the correct statement from the following.

Options

A. Initially electrons will come out from the plate
B. The ejected electrons experience retarding force due to development of positive charges on the plate
C. After some time, ejection of electrons stops
D. None of the above

Explanation

To solve the problem regarding the threshold wavelength and the incident radiation, we can break it down into clear steps:

### Step-by-Step Solution:

1. **Understanding Threshold Wavelength**:
- The threshold wavelength (\( \lambda_0 \)) is defined as the maximum wavelength of incident light that can cause the emission of photoelectrons from a metal surface. If the wavelength of the incident radiation is less than \( \lambda_0 \), photoelectric emission can occur.

**Hint**: Remember that the threshold wavelength is the boundary condition for photoelectric emission.

2. **Analyzing the Incident Radiation**:
- We are given that the wavelength of the incident radiation (\( \lambda \)) is smaller than the threshold wavelength (\( \lambda < \lambda_0 \)). This means the energy of the incident photons is sufficient to overcome the work function of the metal.

**Hint**: Compare the energy of the incident photons with the work function to determine if photoelectric emission will occur.

3. **Photoelectric Emission**:
- Since \( \lambda < \lambda_0 \), photoelectric emission will take place. Electrons will be ejected from the metal surface when the incident radiation hits it.

**Hint**: Recall that the photoelectric effect occurs when photons have enough energy to free electrons from the metal.

4. **Effect of Ejected Electrons**:
- When electrons are emitted from the metal plate, the plate becomes positively charged because it loses negatively charged electrons. This positive charge will create an electric field that exerts a retarding force on the emitted electrons.

**Hint**: Consider the implications of charge conservation when electrons are emitted from the plate.

5. **Conclusion on Statements**:
- Based on the above analysis, we can conclude:
- Statement 1 is correct: Electrons will be emitted since \( \lambda < \lambda_0 \).
- Statement 2 is correct: Ejected electrons experience a retarding force due to the positive charge developed on the plate.
- Statement 3 can be evaluated based on the context given, but generally, if the wavelength is constant, the emission will stop when the energy of the incident photons is no longer sufficient.

**Hint**: Review the conditions under which photoelectric emission ceases.

### Final Answer:
Both Statement 1 and Statement 2 are correct. The photoelectric effect occurs when the wavelength of the incident radiation is less than the threshold wavelength, and the ejected electrons do experience a retarding force due to the positive charge on the plate.