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I was attempting to solve the following problem from IIT-JEE 1991 (actually I first found it on the book Solved problems in Physics)

[Broken]

It asks for the image viewed by an observer at left. Ok, an observer at left would seen an image that passes through a spherical dioptre glass-air only. It doesn't matter the water at the other side, as the been rays going left will NEVER pass trough it after being irradiated by the object. In the same reasoning I would say an observer at right would see an image formed only by a plane dioptre. Happens that the solution in the book considered the image to be secondary (they found a primary image formed when the rays passed trough the spherical dioptre and then used an "apparent distance in glass" formula (that I translate as "plane dioptre"). I really don't know why they used it, and I want to know what is the right answer, as I didn't find anywhere else in internet the solution for the problem.

The book answer is 35cm right of P.

My answer:

2/15 + 1/p' = (1-2)/(-10)

p' = -30cm = 30cm right of P

Thanks

John

[Broken]

It asks for the image viewed by an observer at left. Ok, an observer at left would seen an image that passes through a spherical dioptre glass-air only. It doesn't matter the water at the other side, as the been rays going left will NEVER pass trough it after being irradiated by the object. In the same reasoning I would say an observer at right would see an image formed only by a plane dioptre. Happens that the solution in the book considered the image to be secondary (they found a primary image formed when the rays passed trough the spherical dioptre and then used an "apparent distance in glass" formula (that I translate as "plane dioptre"). I really don't know why they used it, and I want to know what is the right answer, as I didn't find anywhere else in internet the solution for the problem.

The book answer is 35cm right of P.

My answer:

2/15 + 1/p' = (1-2)/(-10)

p' = -30cm = 30cm right of P

Thanks

John

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