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THE DISPERSIVE POWER OF THE MATERIAL OF TWO LENSES ARE IN RATIO 4:3 .IF THE ACROMATIC COMBINATION OF THESE TWO LENSES IN CONTACT IS A CONVEX LENS OF FOCAL LENGTH 60CM,THEN FOCAL LENGTH OF THE COMPONENT LENSES ARE?A,-20CM AND +25 CM,B,-20 AND -25,C,-15 AND +20

Asked by Priyanka 13th November 2017, 4:09 PM
Answered by Expert
Answer:
begin mathsize 24px style p 1 space a n d space p 2 space a r e space d i s p e r s i v e space p o w e r s space f 1 space a n d space f 2 space a r e space f o c a l space l e n g t h s
60 space c m space i s space t h e space t o t a l space f o c a l space l e n g t h

fraction numerator f 1 over denominator f 2 end fraction equals negative fraction numerator p 1 over denominator p 2 end fraction space space
fraction numerator begin display style p 1 end style over denominator begin display style p 2 end style end fraction space equals fraction numerator begin display style 4 end style over denominator begin display style 3 end style end fraction space

fraction numerator begin display style f 1 end style over denominator begin display style f 2 end style end fraction equals negative fraction numerator begin display style 4 end style over denominator begin display style 3 end style end fraction space

f 1 equals negative fraction numerator begin display style 4 end style over denominator begin display style 3 end style end fraction x f 2

t o t a l space f o c a l space l e n g t h
1 over F equals fraction numerator 1 over denominator f 1 end fraction plus fraction numerator 1 over denominator f 2 end fraction


fraction numerator begin display style 1 end style over denominator begin display style 60 end style end fraction equals negative fraction numerator begin display style 3 end style over denominator begin display style 4 f 2 end style end fraction plus fraction numerator begin display style 1 end style over denominator begin display style f 2 end style end fraction

f 2 equals 15 space c m
f 1 equals negative fraction numerator begin display style 4 end style over denominator begin display style 3 end style end fraction x 15 equals negative 20 c m

P l e a s e space c h e c k space o p t i o n space D space i t space s h o u l d space b e space plus 15 c m space a n d space minus 20 c m





space space end style
Answered by Expert 6th December 2017, 4:53 PM
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Tags: lens-formula
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