JKBOPEE GNM LIGHT REFLECTION AND REFRACTION 30 MCQ,S
1. Focal length of plane mirror is
a. At infinity
b. Zero
c. Negative
d. None of these
2. Image formed by plane mirror is
a. Real and erect
b. Real and inverted
c. Virtual and erect
d. Virtual and inverted
3. A concave mirror gives real, inverted and same size image if the object is placed
a. At F
b. At infinity
c. At C
d Beyond C
4. Power of the lens is -40, its focal length is
a. 4m
b. -40m
c. 0.25 m
d. -25m
5. A concave mirror gives virtual, refract and enlarged image of the object but image of smaller size than the size of the object is
a. At infinity
b. Between F and C
c. Between P and F
d. At E
6. In optics an object which has higher refractive index is called
a. Optically rarer
b. Optically denser
c. Optically density
d. Refractive index
7. The optical phenomena, twinkling of stars, is due to
a. Atmospheric reflection
b. Total reflection
c. Atmospheric refraction
d. Total refraction
8. Convex lens focus a real, point sized image at focus, the object is placed
a. At focus
b. Between F and 2F
c. At infinity
d. At 2F
9. The unit of power of lens is
a. Meter
b. Centimetre
c. Diopter
d. M -1
10. The radius of curvature of a mirror is 20cm the focal length is
a. 20cm
b. 10cm
c. 40cm
d. 5cm
11. The plane through the focus perpendicular to the axis of a mirror or lens is
a. Focal length
b. Focus
c. Focal plane
d. Pole
12. Focal length of concave lens is
a. Positive
b. Negative
c. Zero
d. None of the above
13. Focal length of convex lens is
a. Negative
b. Zero
c. Unity
d. Positive
14. In case of spherical mirrors, object distance is taken to be
a. Positive
b. Negative
c. Unity
d. Zero
15. A spherical mirror has focal length-10cm. What type of mirror is it likely to be?
a. Convex
b. Concave
c. Plane
d. None of the above
16. Distances measured perpendicular to and below the principal axis is taken as
a. Negative
b. Positive
c. Zero
d. One
17. The focal length of a lens is -0.4 m. The lens is
a. Convex
b. Concave
c. Cylindrical
d. None of the above
18. The amount of light reflected depends upon
a. The nature of material of the object
b. The nature of the surface
c. The smoothness of the surface
d. All of the above
19. To form an image twice the size of the object, using a convex lens of focal length 20 cm, the object distance must be
a. <20
b >20
c. < 20cm or between 20 cm and 40 cm
d. Cannot say
20. The laws of reflection are true for
a. The plane mirror only
b. The concave mirror only
c. The convex mirror only
d. All reflecting surfaces
21. The unit of refractive index is
a. Meter
b. Degree
c. Dioptre
d. It has no unit
22. A ray passing through which part of a lens emerges undeviated ?
a. Focus
b. Centre of curvature
c. Optical centre
d. Between focus and centre of curvature
23. A full length of the image of a distant tall building can definitely be seen using :
a. a concave mirror
b. a convex mirror
c. a plane mirror
d. Both concave as well as plane mirrors
24. Image formed by a convex spherical mirror is:
a. Virtual
b. Real
c. Enlarged
d. Inverted
25. The focal length of a plane mirror is
a. 0
b infinite
c. 25 cm
d. -25 cm
26. A beam of light incident on a plane mirror forms a real image on reflection. The incident beam is:
a. Parallel
b. Convergent
c. Divergent
d. Not certain
27. Spherical air bubble in water will act as :
a. Concave lens
b. Convex lens
c. Plane-concave lens
d. Plane glass plate
28. A hole is made in a convex lens. Then :
a.A hole appears in the image
b.image size decreases
c. Image intensity decreases
d. No change
29. Critical angle of light passing from glass to air is minimum for :
a. Red
b. Green
c. Yellow
d. Violet
30. A diverging lens will produce
a. Always a virtual image
b. Real or virtual
c. Always real image
d. None of the above
ANSWER KEYS
1. A
2. C
3. C
4. C
5. C
6. B
7. C
8. C
9. C
10. B
11. C
12. B
13. D
14. B
15. B
16. A
17. B
18. C
19. C
20. D
21. D
22. C
23. B
24. A
25. B
26. B
27. A
28. C
29. D
30. B
