If a cell is viewed under low power and them under high power , and no fine adjustment is necessary to see it clearly , the microscope is considered

Options

A. parfocal
B. bifocal
C. achromatic
D. apochromatic

Explanation

To solve the question regarding the type of microscope that allows viewing a cell clearly under both low and high power without the need for fine adjustment, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about a microscope that allows clear viewing of a specimen under different magnifications (low and high power) without needing to adjust the focus.

2. **Identifying Key Terms**: The terms "parfocal," "bifocal," "achromatic," and "apochromatic" are crucial to understanding the types of microscopes.

3. **Defining Parfocal**: A parfocal microscope is designed such that when you switch from one objective lens to another, the specimen remains in focus. This means that little to no fine adjustment is needed when changing magnifications.

4. **Examining Other Options**:
- **Bifocal**: This term typically refers to lenses that have two different optical powers, but it does not specifically relate to microscope functionality in maintaining focus.
- **Achromatic**: This type of lens reduces chromatic aberration but does not guarantee that the focus will remain when switching lenses.
- **Apochromatic**: Similar to achromatic, but designed to bring three colors into focus, it does not imply that the focus remains unchanged when switching lenses.

5. **Conclusion**: Since the question specifies that no fine adjustment is necessary when switching from low to high power, the correct answer is **parfocal**.

### Final Answer:
The microscope is considered **parfocal**.

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