In 'Mesoscopic Physics', we deal with

Options

A. Phenomena at laboratory
B. Molecular phenomena
C. Nuclear phenomena
D. Few tens or hundreds of atom

Answer

To answer the question about what we deal with in 'Mesoscopic Physics', let's break down the concepts step by step:

### Step-by-Step Solution:

1. **Understanding Mesoscopic Physics**:
- Mesoscopic physics is a branch of physics that focuses on systems whose size is between microscopic (atomic and molecular) and macroscopic (large-scale objects).
- It typically deals with systems that contain a small number of particles, usually ranging from a few dozen to a few hundred.

2. **Size and Scale**:
- In mesoscopic physics, the size of the particles or systems is not well-defined or determinate. This means that the particles do not have a fixed size like macroscopic objects do.
- The phenomena studied in this field often arise due to quantum effects that become significant at this intermediate scale.

3. **Comparison with Other Scales**:
- **Macroscopic Physics**: Involves large-scale phenomena that can be observed directly, such as the behavior of solids, liquids, and gases in everyday life.
- **Microscopic Physics**: Involves atomic and subatomic particles, where quantum mechanics plays a crucial role.

4. **Key Characteristics of Mesoscopic Systems**:
- Systems in mesoscopic physics are often characterized by their small number of constituents, which can lead to unique physical properties that differ from those in macroscopic or microscopic systems.
- Examples include quantum dots, nanostructures, and small superconducting devices.

5. **Conclusion**:
- In summary, mesoscopic physics deals with systems that have an indeterminate size and contain a limited number of particles, typically in the range of tens to hundreds. This field explores the unique phenomena that arise in this size range.

### Final Answer:
In 'Mesoscopic Physics', we deal with systems that have indeterminate size and contain a small number of particles, typically ranging from tens to hundreds.