At the Spring Festival party in 2005, a group of deaf-mute youths gave people beautiful enjoyment and good enlightenment with their exquisite dance Guanyin with a thousand hands. (1) as shown in the figure. (1) When performing, all the dancers are in a straight line. According to the knowledge that light travels in a straight line, the audience can only see Tai Lihua, who leads the dance, and can't see other dancers standing behind him.

(2) Different musical instruments have different timbres, and the audience can tell which instrument is making sound even if they don't see the band, which is the reason;

(3) The effect of fog around the stage is achieved by spraying dry ice. When solid carbon dioxide sublimes, it absorbs a lot of heat, and when it is cold, the temperature of water vapor around it decreases, and it liquefies into small water droplets, resulting in the effect of fog.

So the answer is: (1) along a straight line;

(2) timbre;

(3) Liquefaction.