The focal length of the objective lens of a telescope is 50 cm. The magnification of the telescope is 25. We need to find the focal length of the eyepiece.

To find the focal length of the eyepiece, we can use the formula for magnification:

Magnification = (-) Focal Length of the Objective Lens / Focal Length of the Eyepiece

Substituting the given values, we can write the equation as:

25 = (-) 50 cm / Focal Length of the Eyepiece

To solve for the focal length of the eyepiece, we can cross multiply:

25 × Focal Length of the Eyepiece = (-) 50 cm

Dividing both sides of the equation by 25, we get:

Focal Length of the Eyepiece = (-) 50 cm / 25

Simplifying the equation, we find:

Focal Length of the Eyepiece = (-) 2 cm

Therefore, the correct answer is option 3: 2 cm.

Alert - correct answer should be -2 cm: When using the formula for magnification, the negative sign indicates that the image formed by the telescope is inverted.