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Joined:	15 Apr 2007
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8 May 2008 23:39:32 IST

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409

FocalLenght

None

A beaker contains water $\mu$ =4/3 filled to a ht of 32 cms.A concave mirror is fixed 6 cm above the surface of water. An object is placed at the bottom of the beaker & its image is formed14 cms below the surface of water. The focal lenght of the mirror

ans is 12cm

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ashish banga

Blazing goIITian

Joined: 16 Dec 2006

Posts: 1362

8 May 2008 23:47:04 IST

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12cm

apparent depth of the object = real depth/mu
= 24cm
now object distance from the mirror = 24 + 6 = 30 cm
image distance from the mirror = 14 + 6 = 20cm
use mirror equation now with sign
u will get f = -12cm

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