A thin biconvex thin lens is prepared from glass(refractive index=1.5), the two bounding surfaces having equal radii of 25 cm each.One of the surfaces is silvered from outside to make it reflecting.Where should an object be placed before this lens so that the image is formed on the object itself?I have some confusion about sign convention.So,please explain that in this question.
The object should be placed such that the ray after refraction from the first interface appears to come from the centre of curvature of the second surface to the second surface. Second surface will send the ray back and the ray will follow the same path due to the, "Law of Reversibility".
Applying \(\frac{\mu_2}{v}-\frac{\mu_1}{u}=\frac{\mu_2-\mu_1}{R}\) for the first interface:
\(\frac{1.5}{-25}-\frac{1}{u}=\frac{1.5-1}{+25}\)
Now, u can be found which will come out with appropriate sign.
PS: One should ideally specify where exactly the doubt is in own's working.
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Thank you very much ,Sir.