Four double convex lenses with following specifications are available
Lens, A, B, C, D,
focal length, 100 cm, 100 cm, 0 cm, 5 cm,
aperture, 10 cm, 5 cm,2 cm, 2 cm.
Which of the given four lenses should be selected as objected and eyepiece to construct an astronomical telescope and why ? What will be the magnifying power and length of the tube of the telescope ?

Explanation

To solve the problem of selecting the appropriate lenses for constructing an astronomical telescope, we need to consider the specifications of the given lenses and the requirements for the objective and eyepiece.

### Step-by-Step Solution:

1. **Understanding the Requirements**:
- The objective lens should have a **large aperture** to gather more light and provide a clearer image of distant objects.
- The eyepiece lens should have a **small focal length** to provide a higher magnification.

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