Question

What is the focal length of a double concave lens kept in air with two spherical surfaces of radii $R_1=30 \ cm,\ R_2=60\ cm$ and refractive index of glass is $n=1.5$?

• A. 40 cm
• B. -40 cm
• C. 50 cm
• D. -50 cm

Answer 1

Answer: (B)

-40 cm

Answer 2

The correct option is (B): -40 cm.