The reason why the thin cloth is opaque in the dry state is that the fibers of the cloth repel each other due to friction and electrification, so the pores of the cloth are covered by these small "Mao Mao". When the light passes through these small Mao Mao, the light will be scattered and partially reflected, and the light path will be changed. These light rays that change the light path interfere with other incident light, which will further distort the transmitted light, so it is impossible to see the object on the other side through the cloth (so-called opacity, in fact,

When the cloth is wetted by water, because the water is conductive, the charge on the small "Mao Mao" surface of the cloth disappears, and so does the repulsive force. At this time, Mao Mao people will get together honestly and expose the holes in the fabric itself, and then the fabric will be transparent.