A convex lens of focal length f1 and a concave lens of focal length f2 are placed in contact. The focal length of the combination is_____________?

Related Mcqs:

1. Two convex lenses of equal focal length f are placed in contact the resultant focal length of the combination is______________?

   A. zero
   B. focus
   C. 2 f
   D. f/2

2. Dioptre power of an concave lens of 10 cm focal length is_______________?

   A. 10 dioptre
   B. 10 dioptre
   C. 1 / 10 dioptre
   D. 1 / 10 dioptre

3. A convex lens acts as a diverging lens if the_________________?

   A. object is beyond C
   B. if the object is with in C
   C. if the object is within f
   D. both B and C

4. The minimum distance between an object and its real image in a convex lens is_____________?

   A. 2 f
   B. 2.5 f
   C. 3f
   D. 4f

5. Power of a lens is one diopter if its focal length is

   A. 1 meter
   B. 2 meter
   C. ½ meter
   D. ¼ meter

   Submitted by: Rizwan Ayub Saadi

6. The power of a concave lens is_______________?

   A. real
   B. virtual
   C. positive
   D. negative

7. If a convex lens of large aperture fails to converge the light rays incident on it to a single point, it is said to suffer from______________?

   A. chromatic aberration
   B. spherical aberration
   C. both spherical and chromatic
   D. distortion

8. A convex lens gives a virtual image only when the objects lies_________________?

   A. between principal focus and center of curvature
   B. beyond 2 f
   C. at the principal focus
   D. between principal focus and optical center

9. If an object is placed away from 2f of a converging lens then the image will be_______________?

   A. real and erect
   B. virtual and erect
   C. real and inverted
   D. virtual

10. A person wears spectates with concave lenses. It means that normally (when not using glasses), the image of distant objects is focused in his eyes:

    A. behind the retina
    B. in front of the retina
    C. on the retina
    D. on the blind spot

    Submitted by: Abid Hussain