# Silvering of Plano-Convex Lens

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1. Dec 28, 2014

### sarthak sharma

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

can someone please help me out asap as my exams are pretty much close now.....

2. Dec 28, 2014

### sarthak sharma

3. Dec 28, 2014

### ehild

4. Dec 29, 2014

### haruspex

Are you sure? In your diagram, make sure you draw quite modest refractions so that you don't confuse yourself.

5. Dec 29, 2014

### sarthak sharma

@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.....

6. Dec 29, 2014

Yes.