865I think the answer should be x = 15 cm.
5 Answers
1057x=12cm?
Rays become parallel when image is formed at infinity.
66The answer is C. x = 20 cm
Akash Anand Good Work :)
Better if you give the solution as well.Upvote·0· Reply ·2013-02-23 00:54:38
66Applying the lens formula i.e. 1/f=(μ-1)(1r1 - 1r2) we get the focal length 20 c.m. as μ in this case is 1/2 and r2= ∞
Then using 1v + 1u = 1f we get 1u = 1f
as v = ∞ (as the rays are getting parallel), so 1v = 0
So v = f i.e. 20 cm
- Sourup Nag sorry u = 20 cm, not v
865Image and object are in different mediums with different refractive indices. Shouldn't we have to consider this too? In that case, u=20 cm when viewed from water but x is actually 15 cm as r.i. of water is 4/3.