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In a concave mirror, an object is placed...

In a concave mirror, an object is placed at a distance `d_1` from the focus and the real image is formed aat a distance `d_2` from the focus. Then the focal length of the mirror is :

A

`sqrt(x_(1)x_(2))`

B

`(x_(1)-x_(2))/(2)`

C

`(x_(1)+x_(2))/(2)`

D

`sqrt((x_(1))/(x_(2)))`

Text Solution

Verified by Experts

The correct Answer is:
A
Here, `u=f+x_(1), v=f+x_(2)`
use `f=(uv)/(u+v)` and solve to get `f=sqrt(x_(1)x_(2))`
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DISHA PUBLICATION-RAY OPTICS AND OPTICAL INSTRUMENTS-Exercise - 1 : Concept Builder (Topicwise)(Topic 1 : Plane Mirror, Spherical Mirror and Reflection of Light)
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  3. A point source of light is placed in front of a plane mirror.

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  4. In image formatiion from spherical mirrors, only paraxial rays are con...

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  5. Two mirrors are placed at right angle to each other. A man is standing...

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  6. A concave mirror forms the image of an object on a screen. If the lowe...

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  7. A man 160 cm height stands in fromt of a plane mirror . His eye...

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  8. Two plane mirrors are inclined to each other such that a ray of light ...

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  9. When a plane mirror is placed horizontally on level ground at a distan...

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  10. In a concave mirror, an object is placed at a distance d1 from the foc...

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  11. A ray of light is incident at 50^(@) on the middle of one of the two m...

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  12. Two plane mirrors are inclined to each other at a certain angle.A ray ...

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  13. An infinitely long rod lies along the axis of a concave mirror of foca...

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  14. A ray parallel to principal axis is incident at 30^(@) from normal on...

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  15. A car is fitted with a convex side-view mirror of focal length 20 cm. ...

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  16. Two mirrors, one concave and the other convex, are placed 60 cm apart ...

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  17. In Fig. find the total magnification after two successive reflections ...

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  18. A plane mirror is kept parallel to y-axis. A point object is approachi...

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  19. A point object is kept in front of a plane mirror. The plane mirror is...

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