The structure of solids is invested by using

Options

A. cosmic rays
B. X-rays
C. `gamma-rays`
D. infrared waves

Answer

To solve the question regarding which type of radiation is used to investigate the structure of solids, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Types of Radiation**: The question provides several types of radiation: cosmic rays, x-rays, gamma rays, and infrared waves.

2. **Understand the Properties of X-rays**: X-rays are known for their high frequency and high energy. The energy of electromagnetic radiation is given by the formula:
\[ E = h \cdot f \]
where \(E\) is energy, \(h\) is Planck's constant, and \(f\) is the frequency.

3. **Relate Energy to Penetration Ability**: Due to their high energy, X-rays have the ability to penetrate materials, including the crystalline structures of solids. This property is crucial for investigating the internal structure of solids.

4. **Conclusion**: Based on the properties of the different types of radiation, we conclude that X-rays are the most suitable for investigating the structure of solids due to their ability to penetrate and reveal internal structures.

5. **Final Answer**: Therefore, the correct answer to the question is X-rays (Option B).