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![[Post New]](/templates/default/images/icon_minipost_new.gif) 23 May 2007 16:12:06 IST
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Ques. frm raman_shadow ..
A PLANO CONCAVE OF FOCAL LENGTH 10 CM AND A PLANO CONVEX OF FOCAL LENGTH 20 CM ARE KEPT IN CONTACT AND CONVEX SURFACE IS POLISHED .IF REFRACTIVE INDEX OF LENS MATERIAL IS 3/2 ,THEN FOCAL LENGTH OF COMBINATION IS A) -10CM B)-20CM C)ZERO D)INFINITE
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23 May 2007 20:28:12 IST
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I think I have solved this question before here only in goiit????
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Ken
From: UNITED STATES, Green Bay, Wisconsin
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23 May 2007 22:37:23 IST
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even i have solved it yaar.
but i am asking 4 an experts views on it
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Being beaten is often a temporary condition, giving up is what makes it permanent. |
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23 May 2007 22:48:06 IST
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Yeah , you put a lot of effort on the question Raman.
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Ken
From: UNITED STATES, Green Bay, Wisconsin
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24 May 2007 16:13:19 IST
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The method is as follows. The combined focal length of the lenses alone is reciprocal of (- 1/ 10 + 1/ 20). Focal length of the mirror is given by f = 20 ( 3/2 -1) / 2.
Therefore the combined focal length is given by the reciprocal of -1/10 + 1/ 5 = 1/ 10. Therefore the answer is 10 cm but it is positive.
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24 May 2007 22:31:47 IST
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sir i have posted a detailed reply here.
http://www.goiit.com/posts/list/geometrical-wave-optics-lens-10207.htm#58318
please find the flaw in it
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Being beaten is often a temporary condition, giving up is what makes it permanent. |
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