King
A convex mirror of focal length f produces an image half of the size of the object. What is the distance of the object from the mirror?
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Aadarsh
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Use lens formula
King
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1/v-1/u=1/f?
that one?
Aadarsh
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Object distance = -u
image distance = v
Height of image / height of object = v/u
King
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hi/ho=-v/u
King
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can u do it?
Aadarsh
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yeah
King
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yeah as in can u post the sol.?
Aadarsh
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see now,
h / 2h = v/u
u = 2v
King
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ok
Aadarsh
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\[1divv -1divu =1divf\]
King
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\[1/v-1/u=1/f\]
Aadarsh
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|dw:1332858999064:dw|
King
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why is it -2v?
Aadarsh
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Becoz, in calculation, u should take object distance as negative.
So, u becomes -u. And hence -2v
King
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ok so u get 3/2v=1/f
2v=3f
King
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after that?
King
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aadarsh u der?
Aadarsh
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Then, equate v = 3f / 2
Aadarsh
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Substitute it in the formula:
1/v - 1/u = 1/f
King
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i get u=3f
Aadarsh
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U r correct
King
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so that it?
King
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answer is -f
Aadarsh
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Yeah, soorry. Then don't use - 2v in the formula. use 2v. U may get it.
King
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i get u=f
King
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ok.thnx gtg!1
King
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bye
Aadarsh
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Oooooooooooo. Gtg. Byeeeeeeeeeee. ur result?
King
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in what 9th .....94.83%
King
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kk bye!
Aadarsh
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Super. Congrtas. Ready for US trip?????????????
King
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yup!
Aadarsh
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PLz reply to my email. plzzzzzzzzzzz
King
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ok
Aadarsh
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Byeeeee
salini
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@aadarsh,
u have successfully completed 10th so tell me,
can a convex mirror produce an image which is half of the object's height?
Aadarsh
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Arre Shalini didi and king, I think I was in a dream while solving this question. I thought it to be a convex lens instead of a mirror. Here is the detailed answer. Sorry for mistake.
Aadarsh
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Mirror Formula:
1/v + 1/u = 1/f
And, h'/h = -v/u (magnification formula)
So, given, h'/h = -v/u = 1/2............(i)
So, u = -2v.......(ii)
Now, 1/v + 1/(-2v) = 1/f
Or, 1/2v = 1/f
Or, f = 2v
Or, f = 2v
So, f = -u [From (ii)]
salini
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u havent answered my question yet aadarsh can a convex mirror ,
produce an image which is half of the object's height?
i wud like to add one thing here be very clear to visualise the ray diagrams for any lens or mirror b4 solving sum
Aadarsh
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@salini akka, i think a convex mirror can produce an image half size of that of object, in some cases, when object is between infinity and pole of mirror.
salini
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oh my!
check ur 10th book aadarsh
Aadarsh
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didi, its given that it will form a diminished, virtual and erect image. That's all na?????????
salini
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ya so will it produce a half-sized image?
Aadarsh
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not really. BUt can it not produce in some cases???????????????
salini
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i am curious when?
when our bible says no it is a no
u know wat i mean by bible dont u?
Aadarsh
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Yeah, "Bible" means Book. (NCERT) Can u plz say why it cannot?
salini
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its the property of convex mirror to always form virtual diminished(not even the quarter of size of object)_
how?
it was found by great ppl
all we do is read them right?
salini
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whenever u see a question related to lens or mirrors flash the image formation diagrams b4 the formula
@king ur question is wrong
Aadarsh
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How didi? question is wrong? See my process . Everything is correct. But u r true taht a convex mirror cannot form an half image image.
salini
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:)
see ur text book and read my last comment it will help u
Aadarsh
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Yeah, u r rite didi. I was mad at the first itself.