Photo electric effect is the phenomenon in which

Options

A. Photons come out of a metal when it is hit by a beam of electrons
B. Photons come out of the nucleus of an atom under the action of an electric field
C. Electrons come out of metal with a constant velocity depending on frequency and intensity of incident light
D. Electrons come out of a metal with different velocity not greater than a certain value which depends only on the frequnecy of the incident light wave and not on its intersity.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Photoelectric Effect**: The photoelectric effect is a phenomenon observed when light (or electromagnetic radiation) shines on a metal surface, causing the emission of electrons from that surface.

2. **Key Characteristics**:
- The emitted electrons have varying velocities, but their maximum velocity is dependent on the frequency of the incident light.
- There is a threshold frequency below which no electrons are emitted, regardless of the intensity of the light.

3. **Dependence on Frequency**: The energy of the incident photons (light particles) is directly proportional to their frequency. This means that only light above a certain frequency (threshold frequency) can cause the emission of electrons.

4. **Independence from Intensity**: The intensity of the light affects the number of photons hitting the surface but does not affect the energy of individual photons. Therefore, increasing the intensity of light below the threshold frequency will not result in electron emission.

5. **Conclusion**: Based on the characteristics of the photoelectric effect, we can conclude that the correct option is the one that states that electrons are emitted from a metal surface when light of a certain frequency is incident on it.

6. **Final Answer**: After evaluating the options provided, option D is the correct answer.

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