What's the need of a polished surface in a plane mirror?

Question

In a plane mirror, my textbook tells me that in a plane mirror one surface is polished and the other is silvered. If light gets reflected from the silvered surface, why does the polished surface have to be there?

Which textbook, which page? – RedGrittyBrick Jul 20 '15 at 09:04 — RedGrittyBrick, Jul 20 '15 at 09:04
Etching of glass makes it rough. – Harshal Gajjar Jul 20 '15 at 18:12 — Harshal Gajjar, Jul 20 '15 at 18:12

score 1 · Accepted Answer · answered Jul 20 '15 at 10:31

From what I gather you are describing a mirror that is built like

light -> | glass | metal

And your question is, why the glass is polished on the outer side? To suppress unwanted reflections/scattering of the light. If you have rough or textured surface you cannot look through it unhindered and will have additional reflections. This is how your brain is able to see that a surface is rough: there are uneven surface normals leading to bright and dark spots. You don't want any of this in a mirror

So basically, to make the surface smooth for regular reflection. — Dhruv Erry, Jul 20 '15 at 19:07

What's the need of a polished surface in a plane mirror?

1 Answers1