Home
Class 12
PHYSICS
The focal length of a plano-concave lens...

The focal length of a plano-concave lens is -10 cm , then its focal length when its palne surface is polished is

A

`20 cm`

B

`-5 cm`

C

`5 cm`

D

none of these

Text Solution

Verified by Experts

The correct Answer is:
D

`(1)/(f)=(1)/(infty)-(2)/(f_(l))=-(2)/(f_(l))=(1)/(-28)`
`f_(l)=56 cm rArr (mu-1)((1)/(R))=(1)/(56)` .............`(i)`
`((14)/(9)-1)(1)/(R)=(1)/(58)=(280)/(9) cm`
Promotional Banner

Topper's Solved these Questions

  • GEOMATRICAL OPTICS

    RESONANCE ENGLISH|Exercise Exercise-2|62 Videos

  • GEOMATRICAL OPTICS

    RESONANCE ENGLISH|Exercise Exercise-3|80 Videos

  • GEOMATRICAL OPTICS

    RESONANCE ENGLISH|Exercise Problem|33 Videos

  • EXPERIMENTAL PHYSICS

    RESONANCE ENGLISH|Exercise PART -II|10 Videos

  • GRAVITATION

    RESONANCE ENGLISH|Exercise HIGH LEVEL PROBLEMS|16 Videos

Similar Questions

Explore conceptually related problems

A plano-convex lens is made of flint glass, its focal length is

The focal length of a concave mirror is 10 cm. Find its radius of curvature.

The dispersive power of the material of a lens is 0.04 and the focal length of the lens is 10cm . Find the difference in the focal length (in mm) of the lens for violet and red colour.

The radius of curvature of curved surface of a thin plano-convex lens is 10 cm and the refractive index is 1.5 . If the plano surface is silvered, then the focal length will be.

A convex lens A of focal length 20cm and a concave lens B of focal length 10 cm are kept along the same axis with a distance d between them. If a parallel beam, then d is

A convex lens A of focal length 20cm and a concave lens B of focal length 10 cm are kept along the same axis with a distance d between them. If a parallel beam, then d is

In a compound microscope , the magnificent virtual image is found at a distance of 25 cm from the eye-piece . The focal length of its objective lens is 1 cm. If the microspore is 20 cm , then the focal length of the eye-piece lens ( in cm) is .................

The refractive index of a material of a plano-concave lens is 5/3 , the radius of curvature is 0.3 m. The focal length of the lens in air is

For a telescrope, focal length of objective lens is 15 cm and focal length of eye piece is 10 mm. if tube length is 16 cm, then find the magnification.

Focal length of the plano-convex lens is 15cm. A small object is placed at A as shown in figure. The plane surface is silvered. The image will form at

RESONANCE ENGLISH-GEOMATRICAL OPTICS -Exercise-1
  1. A plano-convex lens when silvered in the plane side behaves like a con...

    Text Solution

    |

  2. Define: Radius of curvature and centre of curvature

    Text Solution

    |

  3. The focal length of a plano-concave lens is -10 cm , then its focal le...

    Text Solution

    |

  4. A convex lens of focal length 80 cm and a concave lens of focal length...

    Text Solution

    |

  5. The dispersion of light in a medium implies that :

    Text Solution

    |

  6. Critical angle of light passing from glass to air is least for

    Text Solution

    |

  7. A plane glass slab is placed over various coloured letters. The letter...

    Text Solution

    |

  8. A medium has nv = 1.56, nr=1.44. Then its dispersive power is:

    Text Solution

    |

  9. All the listed things below are made of flint glass. Which one of thes...

    Text Solution

    |

  10. Light of wavelenght 4000 A is incident at small angle on a prim of ape...

    Text Solution

    |

  11. A simple microscope has a focal length of 5 cm . The magnification at...

    Text Solution

    |

  12. In a compound microscope, the intermediate image is

    Text Solution

    |

  13. The resolving power of a telesope is more when its objective lens has

    Text Solution

    |

  14. A Galileo telescope has an objective of focal length 100cm and magnif...

    Text Solution

    |

  15. The convex lens is used in-

    Text Solution

    |

  16. The magnifying power of a simple microscope can be increased, if we us...

    Text Solution

    |

  17. The focal length of the objective lens of a compound microscope is

    Text Solution

    |

  18. Resolving power of a microscope is given by

    Text Solution

    |

  19. An astronomical telescope has an eyepiece of focal-length 5cm. If the ...

    Text Solution

    |

  20. A person with a defective sight is using a lens having a power of +2D....

    Text Solution

    |