13Arrey bhaiya koi toh try maaro, mera chaar page mein bhi answer nahi aaya,,,,,pata nahi kahaan se 3 minute mein karne ka sawaal hai......
[336] ...Am popped up now.....!!!
The dotted part of the lens is cut & kept along the x-axis as shown.
If parallel paraxial rays fall on this system, the coordinate of the image formed after refraction from both the lenses is (30,-1).
If a=2.5 cm, Find "b" & the focal length of the lens.
(Assume that the lens has no Spherical Aberration.)
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7 Answers
13
1first we need to find (b-a)
assuming both are in contact and thin enough and the origin at the optical centre of the 1st lens.
if focal length = f
then net focal lenth = f/2
clearly f/2 = 30 cm => f = 60cm.
also using for the smaller part
m = vu = 1/2
=> x = (b-a)/2
2= b-a => b = 4.5
btw it is definitely not even a 3 minutes q
13I never assumed tht "both are in contact", how have v got the right to use tht (its not even represented in the figure tht way!) ??? [7]
I kept tht part some "d" dist. away n was using all sorts of similarity conditions n was getting 2 bi-quadratics to solve; thts why took me 4 pgs...
btw, answers are right...but do respond to my query...
13The first img. is formed at 60cm (when both of them act as a combination.)
This img. then acts as a virtual source fr the cut part, hence forming the final img. at (30,-1).
So, fr the cut part , u =60, v=30 => m =1/2.
1Assuming ofcourse that the origin was mentioned in your question it would not be possible to calculate anything unless that distance "d" was given...