Important terms related to a spherical lens

Q.

If AB = 10 cm & DB = 40 cm (diameter). What is the radius of curvature & focal length?

1. 40 cm, 10 cm

2. 20 cm, 20 cm

3. 20 cm, 10 cm

4. 40 cm, 5 cm

Q.

If AB = 10 cm & DB = 40 cm (diameter). What is the radius of curvature & focal length?

1. 40 cm, 5 cm

2. 20 cm, 10 cm

3. 40 cm, 10 cm

4. 20 cm, 20 cm

Q.

A & C are centre of spheres. What is the centre of curvature of above convex lens?

1. A & D are centre of curvature

2. A & C are centre of curvature

3. B & D are centre of curvature

4. None of these