The angular magnification of a simple microscope can be increased by increasing :- 1 focal length of lens 2 size of object 3 aperture of lens 4 power of lens

Options

A. Focal length of lens
B. Size of object
C. Aperture of lens
D. Power of lens

Answer

To solve the question regarding the factors that can increase the angular magnification of a simple microscope, we will analyze each option based on the formula for angular magnification.

### Step-by-Step Solution:

1. **Understanding Angular Magnification**:
The angular magnification (M) of a simple microscope is given by the formula:
\[ M = 1 + \frac{D}{F} \]
where \(D\) is the least distance of distinct vision (usually taken as 25 cm for a normal human eye) and \(F\) is the focal length of the lens.

2. **Analyzing Option 1: Focal Length of Lens**:
- If we increase the focal length \(F\), the term \(\frac{D}{F}\) will decrease, leading to a decrease in angular magnification \(M\).
- **Conclusion**: Increasing the focal length decreases angular magnification. (Option 1 is incorrect)

3. **Analyzing Option 2: Size of Object**:
- The size of the object does not directly affect the angular magnification as defined by the formula. Angular magnification is a ratio of angles, and while a larger object may appear larger, it does not change the magnification factor.
- **Conclusion**: The size of the object does not influence angular magnification. (Option 2 is incorrect)

4. **Analyzing Option 3: Aperture of Lens**:
- Increasing the aperture allows more light to enter, which can improve image brightness but does not directly affect the focal length or the angular magnification. The focal length may change due to lens design, but this is not a direct relationship.
- **Conclusion**: Increasing the aperture does not necessarily increase angular magnification. (Option 3 is incorrect)

5. **Analyzing Option 4: Power of Lens**:
- The power \(P\) of a lens is defined as:
\[ P = \frac{1}{F} \]
- If we increase the power, the focal length \(F\) decreases. A smaller focal length will increase the term \(\frac{D}{F}\), thus increasing the angular magnification \(M\).
- **Conclusion**: Increasing the power of the lens increases angular magnification. (Option 4 is correct)

### Final Answer:
The angular magnification of a simple microscope can be increased by increasing the **power of the lens** (Option 4).