Question
Classify the objects or materials given below as opaque, transparent and translucent: 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.