In photoelectric effect, the number of photoelectrons emitted is proportional to :

Options

A. intensity of incident beam
B. frequency of incident beam
C. wavelength of incident beam
D. All of the above

Explanation

To solve the question regarding the photoelectric effect and the proportionality of the number of photoelectrons emitted, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Photoelectric Effect**: The photoelectric effect occurs when light (photons) strikes a metal surface and causes the emission of electrons from that surface. The energy of the incoming photons must be sufficient to overcome the work function of the metal for electrons to be emitted.

2. **Identify Key Variables**: In the context of the photoelectric effect, the key variables are:
- The number of emitted photoelectrons.
- The intensity of the incident light (which relates to the number of photons).

3. **Relationship Between Intensity and Number of Photons**: The intensity of light is directly proportional to the number of photons striking the surface per unit time. Therefore, if the intensity increases, the number of photons also increases.

4. **Link to Number of Photoelectrons**: Each photon can potentially eject one electron if it has enough energy. Thus, if more photons are incident on the metal surface, more electrons can be emitted. Therefore, the number of photoelectrons emitted is directly proportional to the number of incident photons.

5. **Conclusion**: From the above reasoning, we can conclude that the number of photoelectrons emitted is proportional to the intensity of the incident light, which is a measure of the number of photons.

### Final Answer:
The number of photoelectrons emitted is proportional to the **intensity of the incident light** (or the number of photons).