Explain the Junction of bar screens in a wastewater treatment plant.

Why 

 the image in concave mirror is always form real and inverted image 

Concave mirror always form real and inverted image

Difference between concave and convex lens, concave and convex mirror

What is light? What are different types of light ?

I wanted a PDF of the notes but there is no pdf. the topic is reproduction in plants chapter 12 so can you please send a pdf or unable the words to do a copyright or  i have  to write it all please reply  its urgent.....