Classify the objects or materials given below as opaque, transparent or translucent and luminous or non-luminous: Air, water, a piece of rock, a sheet of aluminium, a mirror, a wooden board, a sheet of polythene, a CD, smoke, a sheet of plane glass, fog, a piece of red hot iron, an umbrella, a lighted fluorescent tube, a wall, a sheet of carbon paper, the flame of a gas burner, a sheet of cardboard, a lighted torch, a sheet of cellophane, a wire mesh, kerosene stove, sun, firefly, moon.

Opaque materials (do not allow light to pass through):
1. Piece of rock
2. Sheet of aluminium
3. Mirror
4. Wooden board
5. CD
6. Piece of red hot iron
7. Umbrella
8. Wall
9. Sheet of carbon paper
10. Sheet of cardboard
11. Wire mesh
12. Kerosene stove

Transparent materials (allow light to pass through clearly):
1. Air
2. Water
3. Sheet of plain glass

Translucent materials (allow some light but not a clear view):
1. Sheet of polythene
2. Smoke
3. Fog
4. Sheet of cellophane

Luminous materials (emit light):
1. Flame of a gas burner
2. Lighted fluorescent tube
3. Lighted torch
4. Sun
5. Firefly

Non-luminous materials (do not emit light):
1. All materials except those listed as luminous

This classification helps understand which materials allow light to pass through, whether they emit light, and the distinction between opaque, transparent, and translucent materials.