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S.M.T
S.M.T
07:17
user image
@JohnRennie Hii sir.
In lens , why are diagrams drawn like this.
Why are there two spheres joint together for convex & for concave , none are joined.
Then , there is also another diagram.
user image
John Rennie
John Rennie
07:57
I think the diagrams are just trying to show how lenses are made up from two spherical surfaces. You shouldn't try to read too much into them.
 
1 hour later…
S.M.T
S.M.T
09:12
@JohnRennie K sir.
S.M.T
S.M.T
09:42
@JohnRennie Hii sir.
A concave lens forms the image of an object kept at a distance 20 cm in front of it, at a distance 10 cm on the side of the object.
In this Q
I’m not able to understand what is u ?
image of an object kept at a distance 20 cm in front of it. This statement talks of image of the object & in front on lens which is what happens in concave lens. Image is virtual. v = -20
John Rennie
John Rennie
It's not very clear, but I'd guess it means it forms a virtual image at v = -10. So we have u = -20 and v = -10.
S.M.T
S.M.T
I’m scared of these “not very clear English “ Q if they come in JEE exam.
@JohnRennie Sir , This is not clear.
Because From 1st statement , isn’t it that v=-20 ?
John Rennie
John Rennie
It says "a concave lens" so we know the focal length is negative.
S.M.T
S.M.T
@JohnRennie Yes
John Rennie
John Rennie
And it says "an object kept at a distance 20 cm in front of it".
S.M.T
S.M.T
09:49
@JohnRennie yes sir
shouldn’t we read it like image of an object ?
John Rennie
John Rennie
user image
So this is the lens and the object. Yes?
S.M.T
S.M.T
@JohnRennie yes sir.
John Rennie
John Rennie
And it says the image is "a distance 10 cm on the side of the object"
user image
So it's like this
S.M.T
S.M.T
10:20
Yes sir
@JohnRennie Internet issue sir. I’m back
John Rennie
John Rennie
Hi :-)
So does that make the question clear?
S.M.T
S.M.T
@JohnRennie I got the Q now sir. Thanks a lot.
@JohnRennie Yes.all of it is clear.
John Rennie
John Rennie
:-)

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