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![[Post New]](/templates/default/images/icon_minipost_new.gif) 13 Apr 2008 07:53:08 IST
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Que. - The image formed by a concave mirror is 1/2 in size of the object. If object is placed at 10 cm. from the mirror, where is the imaged formed?
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Ankur
http://www.krazzyankuriit.co.cc/ |
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13 Apr 2008 09:44:12 IST
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for a concave mirror the magnification is given by -v/u..
thus 2 = -v/u..
v= -2u...
so image formed is 20 cm away from the mirror on the +ve side..
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Diamonds r formed under greatest pressures..
so r the champs.
Kriteesh..
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m= hi / ho = - v /u ( u must be knowing that as u r in class x )
 v = - u.hi / ho
as per ur ques, absolute( hi / ho ) is 1 / 2. but image an only be smaller in concave mirror when it is real. so hi/ho is -1 / 2 as image is inverted.
v = - ( - 10 )x(-1/2)
= - 5 cm.
so image is 5 cm in front of mirror ( -ve side ).
Please Note
above answer given by DECODER is wrong bcoz he takes m = 2.
2 reasons why its wrong:
1. if image is 20 cm behind the mirror (+ve) , it is virtual. which means hi  ho for a conacve mirror. but the question says hi = ho / 2.
2. hi < ho is possible in a concave mirror only when absolute( v ) < absolute( u ).
rate me if u found it useful and if it resolved ur queries.
by the way, i too am in class X
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