glass is transparent when the
mirror is ______
Answers
What a mirror actually does? It reflects the light rays incident on it and forms a virtual image in the process.
As per this phenomenon, mirrors can be divided into two groups:
I) Back surface mirror: These are the common mirrors we use in our household; also known as glass mirrors. These mirrors are formed by putting a thin reflective layer of ‘tin and mercury amalgam’ or ‘silver’ on the back side of a transparent front substrate (in common cases glass). Here, the front substrate material must be transparent, as the incident light enters into it from air by refraction, then gets reflected from the metallic back substrate (which must be opaque but polished) and finally again goes through refraction as it comes out in air. Now, some amount of light gets reflected from the air - glass interface itself promotes formation of double imaging. By choosing glass of good quality, this front surface reflection can be kept restricted to 4% of the incident light.
II) Front surface mirror: These are made of highly polished Brass of Bronze as their front surface - which is their reflecting surface as well. Since, no transparent material was used in these mirrors, so these are totally free from any possibility of double reflection. In India, this type of mirror is still manufactured in a village called Aranmulla in Kerala; and the manufactured mirrors are famously known as ARANMULLA KANNADI (literally meaning ARANMULLA MIRROR).