Main cultural relics of transparent mirror

Shanghai History Museum has two transparent mirrors of the Western Han Dynasty, which are round, 7.4 cm in diameter and 50 grams in weight, and the edges of the mirrors are relatively generous. Words and patterns are projected on the back of the mirror. On the one hand, the inscription reads "Clear the interior and make it bright", and on the other hand, it reads "See the light of the sun, landlite". . The mirror surface is slightly convex, which can not only reflect the human face, but also completely reflect the pictures and texts on the back of the mirror to the wall under the irradiation of sunlight, as if the light passes through the mirror body from the back of the mirror and then maps to the wall. Through research, it is considered that the phenomenon of light transmission is caused by many tiny uneven curvature differences on the mirror surface. Graphic mirror is slightly concave, and non-graphic mirror is slightly convex. The light in the concave part converges and the light in the convex part diverges, and there are bright parts and dark parts in the image corresponding to the mirror back picture and text, thus forming the mirror back picture and text on the wall. Some people think that the uneven curvature difference of the mirror surface is caused by casting and polished very transparently; Others think that it is formed by quenching treatment. Transparent mirrors can be made by casting, grinding or quenching. The appearance of transparent mirror shows that the smelting, casting and processing of copper alloy in Han Dynasty have reached a high technical level.