Convex Lenses
  • 1. The principal focus of a convex lens is
A) a point 20 cm away from the lens.
B) the optical centre of the lens.
C) the centre of the curvature.
D) a point where parallel rays converge.
  • 2. The diagram shows four rays of light passing through a convex lens. Which one of the following rays is WRONG?
A) D
B) A
C) B
D) C
  • 3. The image produced at the focal point by a converging lens with an object at a very far distance away from the lens is
A) virtual, diminished and upright.
B) real, diminished and upright.
C) real, diminished and inverted.
D) virtual, diminished and inverted.
  • 4. The image produced by a slider projector is
A) virtual, inverted, magnified.
B) real, inverted, magnified.
C) virtual, inverted, diminished.
D) real, upright, magnified.
  • 5. A convex lens is used to form a sharp image of an object on a screen. Jane covers the top half of the lens with an opaque card. Which of the following statement is true about the new image formed?
A) The top half of the original image will disappear.
B) The whole original image can still be seen but the new image size is half its original image size.
C) The whole original image can still be seen and the new image size is equal to its original image size.
D) The bottom half of the original image will disappear.
  • 6. If the size of the image formed by a converging lens is the same as the object, the object distance is
A) equal to the image distance.
B) equal to the focal length of the lens.
C) less than the image distance.
D) less than the focal length of the lens.
  • 7. The diagram shows an object placed in front of a convex lens.
A) OQ
B) OR
C) OS
D) OP
  • 8. A converging lens has a focal length of 50 mm. At what distance from the lens must a point source of light be placed in order that parallel rays emerge from the lens?
A) 100 mm
B) 50 mm
C) 25 mm
D) 75 mm
  • 9. The focal length of a convex lens is not affected by
A) refractive index of the material used to make the lens.
B) thickness of the lens.
C) distance of the object from the lens.
D) material used to make the lens.
  • 10. If an object is placed 13 cm from a converging lens, the imaged formed is slightly smaller than the object. If the object is placed 11 cm from the lens, the image formed is slightly larger than the object. The focal length of the lens is approximately
A) 6 cm
B) 14 cm
C) 12 cm
D) 5 cm
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