1   what i want to tell you is ....

2 whole content is ......(不改也行）

3before Thomas young  , the thoery that light is the doctrine of the particles is widely accepted.  

    but in 1801, after the experiment of young's, people started to change their idea about this theory
4 young let a light go through double seams,and then there are bright and dark fringes appeared on the screen.

5Thomas young explain to us that light is a a kind of wave which has same frequency,Constant phase difference . when same direction of vibration of the two light beams meet in the space,they will interfere with each other!

应该没问题了