Physical knowledge in Peach Blossom Garden

For the description of the environment of Taohuayuan, we can know that the climate of Taohuayuan is very suitable, and there are few bad weather environments. The protagonist passed a cave before entering Taohuayuan. These two points show that Taohuayuan is in a basin-like environment, just like Sichuan basin, with a suitable climate and a land of abundance. It is appropriate to guess that Peach Blossom Garden is surrounded by mountains, which also explains why Peach Blossom Garden is not easy to be found. 1, sound source: the object making sound. Sound is produced by the vibration of objects. When the vibration stops, the sound generation stops.

2. Media: a substance as a medium of communication. All gases, liquids and solids can carry sound.

3. Sound speed: the speed at which sound propagates in a medium. The speed of sound in solids and liquids is greater than that in air. The speed of sound in air at 15℃ is 340m/s.

4. Echo: the phenomenon that the sound emitted by the sound source hits an obstacle and reflects back to the ear. Only when the echo reaches the human ear more than 0. 1 second later than the original sound can the human ear distinguish the echo from the original sound; Otherwise, the echo and the original sound are mixed together to strengthen the original sound.