Satisfactory explanation of the phenomenon of photo electric effect is based on

Options

A. A. Planck's quantum theory
B. B. Einstein's theory of relativity
C. C. Huygen's wave theory
D. D. Newton's corpuscular theory.

Answer

To solve the question regarding the satisfactory explanation of the phenomenon of the photoelectric effect, we will analyze the options provided and determine which theory best explains this phenomenon.

### Step-by-Step Solution:

1. **Understanding the Photoelectric Effect**:
The photoelectric effect occurs when light (photons) strikes a material (usually a metal) and causes the ejection of electrons from that material. The key points to note are that the energy of the incoming photons must be sufficient to overcome the work function of the material to eject electrons.

2. **Energy of Photons**:
According to Planck's quantum theory, the energy of a photon is given by the equation:
\[ E = h \nu \]
where \(E\) is the energy of the photon, \(h\) is Planck's constant, and \(\nu\) is the frequency of the light.

3. **Threshold Frequency**:
There is a minimum frequency (threshold frequency) below which no electrons are emitted, regardless of the intensity of the light. This indicates that the energy of the photons must be above a certain threshold to eject electrons.

4. **Einstein's Contribution**:
Albert Einstein expanded upon Planck's theory and provided a detailed explanation of the photoelectric effect. He proposed that light can be thought of as being made up of particles (photons), and the energy of these photons is quantized. This explanation successfully accounted for the observations of the photoelectric effect, including the threshold frequency and the kinetic energy of the emitted electrons.

5. **Evaluation of Options**:
- **Planck's Quantum Theory**: This theory provides the basis for understanding the quantization of energy and is fundamental to explaining the photoelectric effect.
- **Einstein's Theory of Relativity**: While important in physics, it does not directly explain the photoelectric effect.
- **Huygens' Wave Theory**: This theory treats light as a wave and fails to explain the particle-like behavior observed in the photoelectric effect.
- **Newton's Corpuscular Theory**: Although it treats light as particles, it does not account for the quantization of energy as proposed by Planck.

6. **Conclusion**:
The satisfactory explanation of the photoelectric effect is based on **Planck's quantum theory**. Therefore, the correct answer is:
\[ \text{A) Planck's quantum theory} \]