Two convex lenses of focal length `20 cm` and `1 cm` constitute a telescope. The telescope is focussed on a point which is `1 m` away from the objective. Calculate the magnification produced and the length of the tube. If the final image is formed at distance of `25 cm` from of eyepiece.

Explanation

To solve the problem, we will follow these steps:

### Step 1: Identify the Given Data
- Focal length of the objective lens, \( f_O = 20 \, \text{cm} \)
- Focal length of the eyepiece lens, \( f_E = 1 \, \text{cm} \)
- Distance of the object from the objective lens, \( u_O = -100 \, \text{cm} \) (the negative sign indicates that the object is on the same side as the incoming light)
- Distance of the final image from the eyepiece, \( v_E = -25 \, \text{cm} \) (the negative sign indicates that the image is on the same side as the outgoing light)

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