# Silvering of Plano-Convex Lens

If the plane surface of a plano-convex lens in silvered then which of the following statements is true?

1. it acts like a convex mirror
2. it acts like a concave mirror
3. it acts like a concave lens
4. no change

my attempt---

the incident ray on the convex surface of the plano-convex will first converge (refract) then reflect from silvered plane surface towards the first surface and then from there it will diverge (refract again) towards the incident side only.

so i came to a conclusion that the combination is diverging on the same side as object and thus it acts like a Convex Mirror

but my book give the answer as a concave mirror and the same answer i get after browsing the net but could not find a proper explanation for it

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ehild
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haruspex
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from there it will diverge (refract again) towards the incident side only.
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Are you sure? In your diagram, make sure you draw quite modest refractions so that you don't confuse yourself.

Are you sure? In your diagram, make sure you draw quite modest refractions so that you don't confuse yourself.
@haruspex i think i kind of get what you want to say that angle of refraction are not very much large.....
so the diagram given above by @ehild would be an ideal diagram
and going by it it is pretty much clear that the incident rays converge on the same side on a point on the pricipal axis and hence it acts like a Concave Mirror
confirm it if you agree.....

haruspex