Question

A convex lens of focal length 25 cm is placed at a distance x from a concave lens of focal length 7 cm. When a parallel beam is incident on the convex lens, it emerges as a parallel beam out of the concave lens. The value of x is

• A. 20 cm
• B. 18 cm
• C. 16 cm
• D. 14 cm

Answer 1

Answer: (B)

18 cm

Answer 2

Here $f_2=x+f_1$ $When\,x=f_2-f_1=18\, cm$