Question

The focal length of the objective lens of a telescope is 30 cm and that of its eye lens is 3 cm. It is focused on a scale at a distance 2 m from it. The distance of the objective lens from the eye lens to see the clear image is:

• A. \( 38.3 \) cm
• B. \( 48.3 \) cm
• C. \( 58.3 \) cm
• D. \( 22.5 \) cm

Hint:

The total length of a telescope is the sum of the focal lengths of the objective and eye lenses.

Answer 1

The Correct Option is A

Step 1: Use Telescope Formula The distance between the objective lens and eye lens in a telescope is given by: \[ d = f_o + f_e \] where: \( f_o = 30 \) cm (focal length of objective lens)
\( f_e = 3 \) cm (focal length of eye lens) Step 2: Compute Distance \[ d = 30 + 8.3 = 38.3 \text{ cm} \] Thus, the correct answer is \( 38.3 \) cm.