When ultraviolet rays fall on a metal plate then photoelectric effect does not occur , it occurs by

Options

A. infrared rays
B. X-rays
C. Radiowave
D. Light wave

Answer

To solve the question regarding the photoelectric effect and its occurrence when ultraviolet rays fall on a metal plate, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Photoelectric Effect**:
The photoelectric effect is the phenomenon where electrons are emitted from a metal surface when it is exposed to light (or electromagnetic radiation) of sufficient energy.

2. **Energy of Incident Radiation**:
The energy of the incident radiation can be calculated using the formula:
\[ E = h \cdot f \]
where \(E\) is the energy of the photon, \(h\) is Planck's constant (\(6.626 \times 10^{-34} \, \text{Js}\)), and \(f\) is the frequency of the radiation.

3. **Work Function of the Metal**:
Each metal has a specific work function (\(\phi\)), which is the minimum energy required to remove an electron from the surface of the metal.

4. **Comparison of Energies**:
For photoelectric emission to occur, the energy of the incident photon (from ultraviolet rays in this case) must be greater than or equal to the work function of the metal:
\[ E \geq \phi \]

5. **Ultraviolet Rays and Their Energy**:
Ultraviolet rays have a certain frequency range. If it is stated that the photoelectric effect does not occur with ultraviolet rays, it implies that the energy of these rays is less than the work function of the metal:
\[ E_{\text{ultraviolet}} < \phi \]

6. **Identifying Other Radiation Types**:
Since ultraviolet rays do not cause the photoelectric effect, we need to consider other types of radiation that have higher energy. X-rays and gamma rays have higher frequencies than ultraviolet rays and thus have more energy:
\[ E_{\text{X-ray}} > E_{\text{ultraviolet}} \quad \text{and} \quad E_{\text{gamma}} > E_{\text{X-ray}} \]

7. **Conclusion**:
Therefore, the photoelectric effect can occur with X-rays or gamma rays, but not with ultraviolet rays if their energy is insufficient.

### Final Answer:
The photoelectric effect does not occur with ultraviolet rays because their energy is less than the work function of the metal. It can occur with X-rays or gamma rays, which have higher energy.

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