Question

The following figure represents two biconvex lenses \( L_1 \) and \( L_2 \) having focal lengths 10 cm and 15 cm, respectively. The distance between \( L_1 \) and \( L_2 \) is:

• A. 10 cm
• B. 15 cm
• C. 25 cm
• D. 35 cm

Answer 1

The Correct Option is C

The distance between two lenses, when both lenses are separated by a distance \( D \), depends on their focal lengths and how they interact. For this setup with two biconvex lenses, the total distance between them \( D \) is the sum of their individual focal lengths:

\[ D = f_1 + f_2 = 10 \, \text{cm} + 15 \, \text{cm} = 25 \, \text{cm}. \]

This configuration ensures that parallel rays entering the system pass through the first lens's focus and exit the second lens as parallel rays, which is a key condition for this lens arrangement.