A converting lens of power 100 dioptre is used as a simple microscope. What is its magnifying power, if the distance of distinct vision is 25 cm.

Answer

To find the magnifying power of a converging lens used as a simple microscope, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Given Data:**
- Power of the lens (P) = 100 diopters
- Distance of distinct vision (D) = 25 cm

2. **Convert Power to Focal Length:**
- The formula for power (P) in terms of focal length (f) is:
\[ P = \frac{1}{f} \]
- Rearranging gives us:
\[ f = \frac{1}{P} \]
- Since the power is given in diopters, we need to convert it to meters:
\[ f = \frac{1}{100} \text{ m} = 0.01 \text{ m} = 1 \text{ cm} \]

3. **Use the Formula for Magnifying Power (m):**
- The magnifying power (m) of a simple microscope is given by:
\[ m = 1 + \frac{D}{f} \]
- Here, D is the distance of distinct vision in cm, and f is the focal length in cm.

4. **Substitute the Values:**
- Substitute D = 25 cm and f = 1 cm into the magnifying power formula:
\[ m = 1 + \frac{25}{1} \]
- Simplifying this gives:
\[ m = 1 + 25 = 26 \]

5. **Conclusion:**
- The magnifying power of the lens when used as a simple microscope is 26.

### Final Answer:
The magnifying power of the lens is **26**.