The magnifying power of a telescope can be increased

Options

A. by increasing focal lengths of both lenses
B. by fitting eyepiece of high power
C. by fitting eyepiece of low power
D. by increasing the distance of object

Explanation

To solve the question regarding how the magnifying power of a telescope can be increased, let's break it down step by step:

### Step-by-Step Solution:

1. **Understanding Magnifying Power**:
The magnifying power (M) of an astronomical telescope is given by the formula:
\[ M = \frac{F_0}{F_e} \left(1 + \frac{D}{F_e}\right) \]
where:
- \(F_0\) = focal length of the objective lens
- \(F_e\) = focal length of the eyepiece
- \(D\) = least distance of distinct vision (approximately 25 cm for a normal human eye)

2. **Analyzing the Formula**:
From the formula, we can see that the magnifying power is directly proportional to the focal length of the objective lens (\(F_0\)) and inversely proportional to the focal length of the eyepiece (\(F_e\)). This means:
- If \(F_0\) increases, \(M\) increases.
- If \(F_e\) decreases, \(M\) increases.

3. **Increasing the Focal Length of the Objective Lens**:
To increase the magnifying power, one way is to increase the focal length of the objective lens (\(F_0\)). This can be achieved by using a larger objective lens.

4. **Decreasing the Focal Length of the Eyepiece**:
Another way to increase the magnifying power is to decrease the focal length of the eyepiece (\(F_e\)). This can be done by using an eyepiece with a shorter focal length.

5. **Using Eyepiece of Higher Power**:
The power of a lens is defined as the reciprocal of its focal length:
\[ P = \frac{1}{F} \]
Therefore, if we use an eyepiece with higher power (which corresponds to a shorter focal length), we can increase the magnifying power of the telescope.

6. **Conclusion**:
Thus, the magnifying power of a telescope can be increased by:
- Increasing the focal length of the objective lens.
- Decreasing the focal length of the eyepiece (or using an eyepiece of higher power).

### Final Answer:
The magnifying power of a telescope can be increased by increasing the focal length of the objective lens and/or using an eyepiece with higher power.