PIC (A) http://imageshack.us/a/img37/941/img20130104192537.th.jpg [Broken] PIC (B) http://imageshack.us/a/img23/5496/img20130104192554.th.jpg [Broken] I hope you can ans it in a simple way as I am just a secondary 6 student :) thx! For pic a, 1. I dun understand why interference occurs when there is 1 slit only. My teacher told me to divide the slit into 2 part. But why ? 2. Does the single slit diffraction happen when the slit is in circular shape ? Will it work when I use the normal one ? ("young single slit") 3. Can the single diffraction be demonstrated in water bath ? Just like the experiment of young double slit in water. 4. Does the single diffraction work for sound wave ? For pic b 1. Why diffraction happen in lens?