When an objects is seen through a calcite crystal, we observe two images. Why ?

With the help of a diagram, explain why the image of an object viewed through a concave lens appears smaller and closer than the object.

Explain, why in daylight an object appears red when seen through a red glass and black when seen through a blue glass?

Through crystallization we can separate

Schottky defect in crystals is observed when

Schottky defect in a crystal is observe when