Lens - Objective Type Questions

1. A convex lens is dipped in a liquid having refractive index same as that of the material of the lens. The lens behave as a 
(a) convergent lens                (b) divergent lens
(c) prism                               (d) glass plate

2. Which of the following will not produce a magnifying system ?
(a) convex lens                      (b) concave lens
(c) concave mirror                  (d) None of these

3. Which of the following can produce a virtual image larger in size than the object ?
(a) concave lens                     (b) convex lens
(c) convex or concave lens      (d) None of the above

4. What is the minimum distance between the convex lens and the object to produce a real image ?
(a) 0                                     (b) f
(c) 2f                                    (d) 4f

5. What is the minimum distance between the object and its virtual image in case of a concave lens ?
(a) 0                                     (b) f
(c) 2f                                    (d) 4f

6.how will the image formed by a convex lens be affected if the central portion of the lens is blackened ?
(a) No image will be formed by the lens
(b) The central portion of the image will be absent
(c) The full image will be formed but it will be less bright
(d) There will be two images, one due to each exposed portions

7.When rays of light fall on a convex lens it
(a) converges them                (b) does not bend them
(c) diverges them                   (d) None of these

8.If there is no atmosphere, the duration of the day would :
(a) increase                           
(b) decrease
(c) remains the same
(d) increase  during winter but decrease during summer

9. When the object is placed beyond the focus of a convex lens, the image formed is :
(a) real                                 (b) virtual
(c) either real or virtual          (d) none of the above

10. What is the minimum distance between an object and its real image formed by a convex lens ?
(a) 0                                    (b) f
(c) 2f                                   (d) 4f

11. A convex lens of focal length 32 cm forms a virtual image of double the size of the object. What is the distance of the object from the lens.
(a) 16 cm                            (b) 32 cm
(c) 10 cm                            (d) None of the above

12. The field of the view is maximum for
(a) plane mirror                  (b) concave mirror
(c) convex mirror                (d) parabolic mirror

13. A convex lens is immersed in a liquid denser than glass. It will behave as
(a) plane glass                   (b) diverging lens
(c) converging lens             (d) None of the above

14. Half of the lens is wrapped in black paper. How will it change the image ?
(a) Size of the image is halved.
(b) Intensity of image is halved.
(c) No change in size of image or intensity.
(d) None of the above

15. For which color, the focal length of a convex lens is more ?
(a) Red                              (b) Green
(c) Yellow                           (d) Blue

16. In which case the image formed by a concave lens is real ?
(a) 0 < u < f                      (b) f < u < 2f
(c) 2f < u < ∞                   (d) None of the above

17. In which case the image formed by a convex lens is virtual ?
(a) 0 < µ < f                      (b) f < µ < 2f
(c) 2f < µ < ∞                   (d) None of these above

18. A decrease in aperture of a lens changes the
(a) Size of the image         (b) Position of the image
(c) both position and size   (d) intensity of the image

19. An object is placed at infinity. The image formed by a concave lens is always
(a) At focus
(b) Between F and 2F 
(c) Beyond 2F
(d) Between focus and optical centre

20. A convex lens becomes less converging when placed in 
(a) oil                              (b) water    
(c) both (a) and (b)          (d) None of the above

21. As an object gets closer to the focal point of a convex lens from infinity, its image
(a) becomes smaller
(b) is magnified
(c) becomes closer to the lens
(d) becomes farther from the lens

22. On decreasing the radii of both the surfaces of a double convex lens or double concave lens, its focal length will
(a) decrease
(b) increase
(c) neither increase nor decrease
(d) remain same

Answers :
1. d
2. b
3. b
4. b
5. a
6. c
7. a
8. b
9. b
10. d
11. a
12. c
13. b
14. b
15. a
16. d
17. a
18. d
19. d
20. a
21. d
22. a