The first electron microscope was designed by

Options

A. Janssen and Hans
B. Robert Hooke
C. Knoll & Ruska
D. Schleiden and Schwann

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the inventor of the first electron microscope. It is important to differentiate between various types of microscopes and their inventors.

2. **Analyzing the Options**: The options provided are:
- Janssen and Hans
- Robert Hook
- Noll and Ruska
- Silden and Swan

3. **Evaluating Each Option**:
- **Janssen and Hans**: They are credited with inventing the first compound microscope in 1590, not the electron microscope.
- **Robert Hook**: He designed a simple microscope and is known for discovering cells, but he did not invent the electron microscope.
- **Silden and Swan**: These scientists contributed to cell theory but were not involved in the invention of the electron microscope.
- **Noll and Ruska**: They are recognized for creating the first operational electron microscope in 1932.

4. **Identifying the Correct Answer**: Based on the analysis, the correct answer is Noll and Ruska, as they developed the first functional electron microscope.

5. **Conclusion**: The first electron microscope was designed by Noll and Ruska in 1932.

**Final Answer**: Noll and Ruska

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