A concave lens produces an image 20 cm from the lens for an object placed 30 cm from the lens. The focal length is
  • -40 cm
  • +60 cm
  • -60 cm
If a, b, c and d represent object distance, image distance, focal length and radius of curvature in case of a spherical mirror, then:
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  • A
  • B
  • C
  • D
The maximum image distance in case of a concave lens of focal length 'f' is :
  • 2f
  • 3f
  • f
  • 4f
If the image formed by a concave mirror is observed to be virtual, erect and larger than the object then the position of the object will be
  • between infinity and centre of curvature
  • between the pole of the mirror and its principal focus
  • at centre of curvature
  • between the focus and centre of curvature
SI unit of power of lens is
  • Micrometre
  • Dioptre
  • Kilometre
  • Metre
0 h : 0 m : 1 s

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