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

Related Mcqs:

1. 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_____________?

   A. f2 + f1
   B. f2 – f1
   C. f1f2/f2+f1
   D. f1f2/f1-f2

2. 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

3. 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

4. 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

5. Unit of power of a lens is________________?

   A. meter
   B. watt
   C. diopter
   D. horsepower

6. The power of a concave lens is_______________?

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

7. 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

8. A wire obeys Hooks law is of length 11 when it is in equilibrium under a tension F1. Its length becomes 12 when the tension is increased to F2. The energy stored in the wire during this process is____________________?

   A. (F1+F2) (121+122)
   B. (F1+F2) (122-112)
   C. (F1+F2) (12-11)
   D. (F1+F2) (12-11)

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 point where the incident parallel rays of light converge or appear to diverge after passing through a lens is called______________?

    A. center of curvature
    B. focus
    C. optical center
    D. aperture